Tonight, Tesla makes its cars autonomous. Well, semi-autonomous. And it did it with an over-the-air update, effectively making tens of thousands of cars already sold to customers way better.

There are two things to talk about here. There’s the small story about the features and what the upgrade actually looks like and how it works. That’s a good place to start: This is the biggest change to the visual display of the Model S and X ever. There are new instrument panels, app windows are larger and take up more of the 17-inch touchscreen. Drivers will now get more information about what their cars are doing when in Autopilot, they can lock and unlock their car from the status bar. There’s a new clock!

These are simple cosmetic changes. The Big Story is that all of this—and really, who cares about anything beyond autopilot mode?—is being pushed through to customers' Teslas overnight. The update will begin being pushed out tonight, and will hit every Tesla made and sold in the US in the past year over the course of this week.

Before you get too excited about an autonomous, hands-free present, you need to know that you can’t nap in the back, chauffeured around in beautiful, electric silence.

Even in Autopilot, you keep your hands on the steering wheel. Well… you don’t have to keep your hands on the steering wheel. You can rest them on your knees (resting on knees, palms up, fingertips touching the wheel is advised), or keep one pinky on the wheel. And okay, you can take your hands off altogether for a moment. But after a few seconds, your car will give you a little message, asking you to touch the wheel in some capacity.

If at any point you grab the wheel, Autopilot will turn off, passing control back to you. The wheel doesn’t have capacitive touch, but it measures torque, so any tiny little movements you make against it, it feels and knows you’re there, and at least sort of responsive. But again, you only have to touch it if you want to—unless you’re in New York, then you’re legally required to have one hand on the wheel.

"We tell drivers to keep their hands on the wheel just in case, to exercise caution in the beginning," Elon Musk said today at a press event. "Over time, long term, you won't have to keep your hands on the wheel—we explicitly describe this as beta."

Obviously, there are legal reasons Tesla can’t let you just go totally hands free. There are different regulations all over the country, and stricter ones in Europe, where the company has a large consumer base. TL;DR, this is Tesla’s way of keeping you responsible for your car (and keeping lawyers off its back).

Still, it’s a fairly aggressive attitude, especially compared to the pokey pace at which other automakers have rolled out similar tech. "Regulators need to see clear evidence that the reliability is there," says Musk. "It works almost to the point where you can take your hands off," Musk laughs, "but we won't say that. Almost."

It will get more and more refined over time. Eventually, we want it to automatically have your car put itself to bed in your garage. Tesla Motors CEO Elon Musk

So that’s all sort of what it doesn’t do—here’s what it does. Autosteer, the beta feature of Autopilot that's being pushed to the Model S and X, uses real-time feedback features and a suite of sensors—-a front-facing radar, a camera with image recognition capability, and 360-degree ultrasonic sonar—-to read lane lines and detect other vehicles. Based on that info, the car steers itself and maintains a safe speed.

So will this sensor suite be enough to enable autonomous driving eventually? In a word, no. "This is not the full autonomy sensor suite," says Musk, though he doesn't believe a fully autonomous vehicle requires LIDaR, which is what Google and other automakers use on their autonomous prototypes. "I'm not a big fan of LIDaR, I don't think it makes sense in this context," though he admits his other company, SpaceX, uses it for its spacecraft technology.

This software update won't work everywhere you go. It’s really for highway and freeway driving—you have to be going at least 18 mph for it to work—where conditions are pretty predictable and driving doesn't get too complicated. More confusing things, like construction, cyclists, garbage cans, errant pets, and traffic lights will still require human piloting to navigate. But long stretches of uneventful road can be relatively hands-off (except for the fact that they are technically hands on).

To change lanes, you simply select the respective turn signal, and the Model S does the rest—this feature is called Auto Lane Change; it’s off by default. When I tried the feature, I was told you need to still check your blind spots (you know, like a driver should), and then just hit the turn signal to tell your car where to go. But if there is something in the way, the car simply won't budge. If it's all clear, the car speeds up as it moves over, the way most drivers would.

“The [human] pilot still makes the decision,” says Ricardo Reyes, Tesla’s head of comms. “The car can say ‘something is happening, please pay attention,’ if something happens. We call it ‘Autopilot’ for a reason—you’re still in control here. It’s like a plane: It goes into autopilot, but the pilot still does things like takeoff and landing.” If you start to zone out or fall asleep (which, some of us—points to self—already do while actively driving), the car will beep at you until you take back control.

And if you don’t take back control, there’s a backup procedure. After flashing a message telling you to take hold of the steering wheel and a series of beeps, if you still aren’t taking over, the car will eventually slow to a stop and put your hazard lights on. Audi and Daimler do the same thing in their prototype systems.

The Model S and Model X can also now parallel park for you. Self-parking is an increasingly common feature even in non-luxury cars, but it’s nice to know you won’t ding your new Tesla trying to back into that space.

These are advanced features, to be sure, but Tesla’s not leading the auto industry with the ability to keep a car in its lane and away from other cars—the Mercedes first offered that in Germany with the 2014 S-Class.

What sets Tesla apart from its pseudo-autonomous driving competitors is The Big Story. The fact that Tesla is pushing all of this via an over the air software update is a huge difference to how other manufacturers, like Honda, Audi, and Mercedes, are going at the same technology. When the update goes out, anyone who’s bought a Tesla made in the past year (Tesla started equipping cars with the necessary sensors in September 2014) will just wake up to an essentially brand new, more capable system. The cars get better as they age. (Sorry early adopters, there’s no way to retrofit the necessary hardware onto older cars to make them drive themselves.)

Reyes says this forward-thinking attitude means there are also hardware differences that set Tesla apart: Tesla started including the necessary hardware more than a year ago, and that its more central operating system makes such upgrades easier. Other manufacturers have a more piecemeal methodology, building a piece of technology that can do this thing and then putting that physically into the car. “In other cars, all the systems work separately—there are different processors for different parts: the safety system here, the cruise control here,” says Reyes. “And that’s the evolution of building cars in stages, whereas our car has a central operating system, more like what your phone has.”

"Car-makers need to think of their cars as connected devices, that the way a car should operate, like your cell phone or laptop so you can do improvements over the air," says Musk. "It's important for safety and functionality that car-makers move to a connected philosophy ... It's kind of odd to have a computing device that's not connected."

That’s the type of thing that will likely play a bigger role going forward than it does right now: Keeping a car in its lane and away from other vehicles is relatively simple, as far as autonomous technology goes, but the bigger idea is that vehicles move to this connected system mentality, you can make all sorts of changes on the fly, as you learn and evolve. Not that other automakers don't know that. "Connected" might be the most important buzzword in the industry right now, though Tesla's undeniably ahead of the curve.

The fact that Tesla's fleet is connected and receives real-time feedback means the company can continuously make Autopilot smarter. Back in July, Musk complained that the crummy lines on the 405 Interstate around LA made it difficult testing ground for Autopilot (the car's camera had trouble reading them).

Now, as more and more Model S and X cars hit the roads, they will record and relay the information on highways and freeways across the fleet, creating a car-crowdsourced database of road conditions.

Still, Musk says, "we really need better lane markings in California." He notes Autopilot works best in places where the road markings are very visible, or in traffic, where things move slowly. He emphasizes the importance of the fleet intelligence in creating an autonomous driving system that can succeed—which, of course, brings up questions about his stated concerns over the rise of AI. "If I'm so afraid of AI, why am I doing this?" he joked. "I don't think we have anything to be afraid of with cars driving themselves, they're not going to take over the world... that's a deeper AI, some sort of AI that due to itself or people, tries to drive civilization in a direction that is not good." Long story short, don't worry about your Model S killing you.

Rise of the robots aside, Musk and Tesla are future-facing. "This version of Autopilot does not take into account stop signs and red lights, but a future software update will," Musk says. "It will get more and more refined over time. Eventually, we want it to automatically have your car put itself to bed in your garage." He says full autonomy will be here from Tesla in three years, which puts it ahead of the 2020 deadline proposed by Google, Nissan, and Mercedes. (Though regulatory approval will vary.)

For now, it's (almost) hands-free driving and lane changes. But that's a huge jump for people who spend long hours on the highway, especially in slow-moving traffic. And it's just for now. "I think this is going to be quite a profound experience for people," says Musk. "I think it's going to change people's perceptions of the future, quite rightly."