What it means: Recap – a customs union is an agreement that would allow Britain to keep trading with EU countries without tariffs (i.e. extra taxes on British goods in EU countries) as long as Britain continued to place EU tariffs on goods from non-EU countries. Theresa May wants one, but most of the cabinet doesn't, because they say it's basically reversing Brexit.
If Amber Rudd, the former home secretary, were still around, May would probably have just managed to pass this. But her replacement, Sajid Javid, is backing the hard Brexiteers. They've come up with a model they call 'max fac', which stands for 'maximum facilitation', and apparently uses 'new technology' to make border control much easier... how, you ask? Who knows, but they're convinced it wil.
Now, May and her team are back at the drawing board, apparently coming up with a new idea called the 'hybrid plus' model which will somehow make everyone happy. If they think the high-tech sounding names are gonna fool us into thinking this whole process is super slick and smooth, well, they're wrong... nice try guys.