What are the 'snapback' nuclear sanctions the UN will reimpose on Iran?

UN sanctions on Iran that were lifted as part of a landmark 2015 nuclear deal will come back into force at midnight after the "E3" European group – Britain, France and Germany – alleged that Tehran was not meeting its obligations, triggering a "snapback" mechanism integrated into the deal. Here are some key facts about what sanctions are involved. 

What are the 'snapback' nuclear sanctions the UN will reimpose on Iran?
UN sanctions on Iran that were lifted as part of a landmark 2015 nuclear deal will come back into force at midnight after the "E3" European group – Britain, France and Germany – alleged that Tehran was not meeting its obligations, triggering a "snapback" mechanism integrated into the deal. Here are some key facts about what sanctions are involved.