The Stacks project

113.12 Things you always wanted to know but were afraid to ask

There are going to be lots of lemmas that you use over and over again that are useful but aren't really mentioned specifically in the literature, or it isn't easy to find references for. Bag of tricks.

Example: Given two groupoids in schemes $R\Rightarrow U$ and $R' \Rightarrow U'$ what does it mean to have a $1$-morphism $[U/R] \to [U'/R']$ purely in terms of groupoids in schemes.