(CNN) The European Union is arguably the world's most powerful bloc. But it's about to lose the United Kingdom, one of its biggest members. Just how and when the UK leaves the EU will have implications that ripple around the globe.

So, you've heard about Brexit but haven't been keeping up with every twist and turn of the developments. (We get it. You're busy.)

No worries. Here's everything you need to know to become an insta-pundit.

What is Brexit?

Britain + exit = Brexit. It's the idea (once unthinkable) that the Brits will leave the European Union. But in a stunning result the United Kingdom voted to do just that in a bitterly fought referendum in June 2016.

Since then it's been talks, disputes, finger-pointing and threats -- just like your typical divorce.

But the UK and the EU finally might have reached an agreement in which they can finalize their split.

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How does it impact the rest of the world?

If you're a European nation: You have the most to lose -- on so many fronts. Just under half of the UK's exports go to the EU. Just over half of its imports come from the other 27 nations in the bloc. All of that is now up for a (painful) renegotiation. Then, think about diplomacy. Whenever Europe's done something useful on that front, the UK -- a serious military power -- has often been in the driver's seat. So, the EU is losing a heavyweight.

If you're the US: The world's already dangerous and volatile enough. Some in the United States may worry that the unraveling of the union -- a vital ally -- will unleash more instability. The UK's also America's seventh-biggest trading partner. Why rock the boat on such a sweet status quo?

If you're any other nation: The UK is the fifth biggest national economy in the world. Think of the effect Brexit will have on the world's markets. Even if they don't collapse, the uncertainty is bad enough. Markets, you see, love stability. And unstable markets = potential bad news for your country's economy.

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Ok, wait. Before we go any further: What's the difference between England, Great Britain and the United Kingdom?

We sometimes use them interchangeably (and incorrectly). So, here's a quick geography lesson.

The United Kingdom is not a single country but a country of countries. It's made up of four nations:

England

Scotland

Wales

Northern Ireland

Great Britain is the island that holds England, Scotland and Wales.

And England is the big dog. It's the most populous part of the UK and holds its capital, London.

And what's the EU?

The European Union is a bloc of 28 countries that decided it would be cool if its citizens could go about vacationing and trading with each other without worrying about all the red tape.

Its roots date back to the period after World War II. After six years of fighting, Europe was decimated. Economies were in the toilet. Old enemies had to accept the fact they needed to live with each other (like France and its old occupier, Germany). So, little by little, countries started forming partnerships.

By the 1990s, we had the modern European Union. It represents half a billion people.

The idea is: If you're linked economically, you're less likely to bicker and fight.

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Sounds like a great idea. So, what's the problem with the EU?

It sounds like a happy marriage. But you know how that goes. When world events walk in, these countries all react differently. They fight over how to deal with refugees coming to their shores. They can't agree on financial matters. They're mad that some of them have to pony up more than others to bail out countries that are doing terribly. And this has given rise to anti-EU parties all across Europe.

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Has a country ever left the EU before?

No country has, but the world's largest island did. Greenland, which is part of Denmark, was part of the EU until it left in 1985. (The rest of Denmark stayed.)

The UK will be the first bona fide country to leave. Greece has thought seriously about it, though. That would be Grexit (another story altogether).

But think about the precedent that's about to be set. When the UK leaves, other EU countries might start eyeing the door too. That means the EU could slowly fall apart. And that could have huge consequences for the economy and stability. (Remember when we talked about why the EU came into being in the first place?)

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It's been two years since the Brits voted 'yes' on Brexit. What's the holdup?

Turns out untangling a 45-year marriage is not as easy as the Brexiters claimed it would be. The fear of creating some serious unintended consequences (economic or otherwise) is high, and many hurdles have yet to be overcome. The delays, the dangers and the constant bickering are now -- just two months before Britain is due to leave -- prompting some who voted for Brexit to change their minds, opinion polls suggest. Remember all those Brits Googling "What is Brexit?" the day after they voted for it?

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What's happening now? Why's Brexit back in the news?

They've been trying to hammer out a divorce deal, since the UK soon will be outside of the EU trading block. The thought of the UK tumbling out of the EU without a future trade deal scares the living daylights out of business people in Britain and all across Europe. The negotiations have been tough sledding. But finally, after more than two years of wrangling, they came up with this: a draft agreement (in an easy-to-read 585 pages ) that laid out how the UK will leave the EU on Friday, March 29, 2019.

But, under that plan, the UK would stay inside the EU's single market and still be subject to EU laws and regulations until the end of 2020. That would give everyone enough time to ... hammer out a future trade deal. So yes, probably two more years of the same.

So, essentially the UK would leave the EU by basically staying in it for another two years. That's clear, right?

Oh, one other important thing: The agreement guarantees protections for the more than 3 million EU citizens in the UK, and over 1 million UK nationals in EU countries to continue to live, work or study as they currently do.

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What's one of the biggest sticking points?

The Irish "hard border." Right now, the border between the Republic of Ireland and Northern Ireland is open. People (and trade) move between the two nations with ease. There are fears that could change in a Brexit divorce. The Republic of Ireland is in the EU. But Northern Ireland, which is part of the UK, won't be in the EU trading bloc after the split. Normally that would require a so-called "hard border," with checkpoints, border crossings and other infrastructure. Those could seriously slow trade and other economic activity.

Irish politicians also fear they could escalate tensions and raise the need for security to be in place. (No one wants a return of the Troubles in which more than 3,600 people were killed.) Pro-Brexit types in Great Britain would be OK with a hard border if it means the UK can negotiate its own trade deals with other countries. So, the draft agreement maintains the status quo on the Irish border while the two sides work out a permanent solution.

Still confused? Here, we'll explain it with Lego.

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So did the agreement pass?

Nope. On January 15, the UK Parliament voted a resounding rejection of Theresa May's proposed Brexit plan. At 432 to 202, it was a historic defeat, with more than a hundred "no" votes cast by members of May's own party.

The resounding defeat even led Jeremy Corbyn, leader of the opposition Labour Party, to trigger a vote of no confidence in Theresa May, which could have led to a general election. But May survived the vote, clinging onto power by the skin of her teeth -- yet again.

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What next, then?

May is still trying to salvage her deal, and could put it before parliament again with a few tweaks -- but it doesn't look likely that any version of her agreement would be able to pass. In theory, then, Britain would end up leaving on March 29 under the "no deal" scenario that businesses are fretting so much about.

But parliament might even block that from happening, and instead force May to extend Article 50 -- essentially kicking the can down the road, and making that date circled in red on the Brexit calendar pretty irrelevant after all.

That would give everyone more time to figure out a way forward -- whether it's holding more votes on May's deal, securing a dramatically new agreement or throwing it all back to the people, in the shape of a general election or second referendum.

And then there's the nuclear option -- Britain could, technically, revoke Article 50 and pretend the whole thing never happened. That's according to the European Court of Justice, which ruled in December that such a move would be legal. But that would hugely anger the millions of Brits who voted for Brexit -- so don't expect May to take that path any time soon.

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Will there be a re-vote on the referendum?

Some big-time Brits like former PM Tony Blair have been calling for this, but no, there are currently no plan to take this back before voters. British Prime Minister Theresa May has slammed the door shot on that idea, saying a new vote would be a "gross betrayal" of democracy. Her draft agreement will be voted on by the parliaments of the UK and the EU, and that's that, she's said.

That said, the campaign for a second go -- also being called a People's Vote -- has gathered pace, especially since May's deal was so emphatically defeated. Plenty of Labour MPs have been lobbying Corbyn to support it, and if that happens, it could start looking like the easiest way out of the mess.

Still, parliament would have to approve a second referendum and decide what options it would entail -- which could itself be a lengthy process.