Begging the question: What exactly does "ceasing to be a member of the European Union" mean? What I mean is, there was a whole sales pitch during the campaign

Begging the question: What exactly does "ceasing to be a member of the European Union" mean? What I mean is, there was a whole sales pitch during the campaign about what it might mean (e.g. more money for the NHS) which we all found out subsequently to be tosh. Now we have: "Free trade but not free travel" or something to that effect. Never was such detail ever discussed prior to the referendum.