Now that Brexit will happen (hopefully!), we're finally onto the real deal, the free trade agreement. This thread is the successor to Will Boris get Brexit done?.
In summary, most trade agreements between countries involve some form of alignment between countries' standards to enable trade to be done. In our case, the UK is already fully aligned with EU standards and the negotiations ahead are about how much the UK diverges from the EU after Brexit.
The European Commission has been briefing euro countries over the last few days on what they call the "level playing field," which will become the big row between the UK and EU this year. The EU fears that the UK could become like Singapore with lower taxes and standards and attract businesses away from EU countries. They have stated that if the UK wants full access to EU markets, then we must maintain the same standards as the EU today, but also that we align ourselves to future EU standards too. Something Boris has already ruled out.
If we agree to accept future EU law and standards, that is not leaving. Isn't Brexit meant to be about leaving the EU?