Microsoft CEO Satya Nadella Business Insider First, we had the PC. Then we had the browser.

Next, Microsoft CEO Satya Nadella thinks it will be the "agent," the sort of virtual assistant like his company's Cortana that controls the apps on our phone or computer for us.

"To me, AI is going to happen," Nadella said, on-stage at the O'Reilly Next:Economy summit. "It's technology that's inevitable."

To Nadella, the new wave of "agents", or AI-assisted services like Cortana or Siri, are going to change how we browse the web.

It's still browsing, but it's different because you're not invoking every app, Nadella said. Instead, if someone asks "do I need to bring an umbrella today?" it will be the agent who knows your location and can look up the weather to see if it's raining and say yes or no.

To Nadella, the future will be a lot of people walking around talking to their agents naturally. "'Hey Cortana' is in my vocabulary. Having that become more pervasive is my pursuit," Nadella said.

Microsoft isn't the first to consider this a marked change in user interface and how people will interact with computers.

Earlier at the event, Facebook's AI guru Alexandre Lebrun and Siri's original creator Adam Cheyer took issue with the notion that these tools are for the elite.

Both argue that these "virtual assistants" are just new ways of interfacing with a computer. First came the keyboard and the mouse, and next it will be using natural language, Lebrun explained.

Cheyer used the example of needing to pick up a bottle of wine that pairs well with a lasagna en route to his brother's house. If you wanted to do that yourself, you'd need to determine what wine pairs well with lasagna (search #1) then find a wine store that carries it (search #2) that is on the way to your brother's house (search #3). Once you have that figured out, you have to calculate what time you need to leave to stop at the wine store on the way (search #4).

Instead, Cheyer's new company, Viv, is designing an "assistant" which can string all those answers together using artificial intelligence and give you the right answer. These assistants are designed to save time like a traditional assistant does, but they're also fundamentally changing how you would interact with your phone, your watch or your computer, Cheyer said.