In simple terms, on 23 June 2016....a referendum was 'allowed' by the right-leaning government on whether the UK should stay as a member of the EU. When you go back to the early 1970s....as the membership was concreted in.....there wasn't that much of a thrill with the public. The leadership figured this vote would be a 55-to-60 percent 'remain in the EU'. They guessed wrong....it was 52-percent to exit.
The government then spent roughly eight months mostly 'grinning' at folks and trying to find some exit to the referendum. The bitterness shown by the pro-EU Europeans (the French, the Germans, etc)? They went way beyond what you'd expect and that really didn't help matters. On 29 March 2017.....notice was finally given. They would follow the set path that the EU has to exit. Basically, you have a two-year exit period to negotiate all the little pieces to still do business....travel without a visa....handle banking transfers....etc. Along the way, the EU wanted the UK to pay 'damages' (this got into the hundreds of billions of Euro 'talk').
At some point, all of this negotiation chatter went negative, and the treaty product seemed to be worthless. To be honest, this hype about paying the EU some kind of money....made it seem like paying a 'whore' for services.
At this point, a 'hard' BREXIT versus 'soft' BREXIT started to get discussed. This meant that if you reached the deadline (the EU Constitution says you could exit with no treaty and find things very messy if you wanted to conduct trade), you would be screwed. A 'soft' BREXIT meant a treaty existed.
The vote last night in the UK? The Prime Minister had the treaty and folks had a chance to read the requirements. A vast majority (way more than a handful of votes, actually 200 votes more than necessary) said NO.
What happens now? The EU is sitting there and shaking its head. They refuse to give any real deal situation to the Brits. Adding to the EU pain....the election in May for EU representatives across Europe will be affected by this event.
Could another referendum be held? Yes. Some suggest that 55-to-60 percent would vote to stop the BREXIT. Course, it might be another 52-percent in favor of leaving the EU.
How this might end? It is possible that it goes to a messy end, and President Trump arrives in March 2019....to offer up a major trade deal with the US, and engage in some deals that go way beyond what the EU could ever put on the table.