Carl Bildt, former Prime Minister and Foreign Minister of Sweden helps us navigate Brexit:

Brexit day is here! What happens now?

Well, on Friday, what happens is that all of the UK representatives leaves everything in Brussels. All of the meetings, all of their coordination, all of the commissions and whatever, when it comes to shaping and taking the common decision. So legally, they leave. But they remain within the legal framework of the European Union. All of the laws, all of the regulations will apply to them for the entire year. They remain in the Customs Union. They remain in the single market. And the reason for that is that one would have to try to negotiate an arrangement between the United Kingdom and the EU during this year.