Use this tag when you are talking about gluing pages together in some certain order for the purpose of more effective printing.
Imposition is about how to glue pages of the document together in order to print them more effectively. For example, when you want to print two-sided A4 booklet on the A3 paper. Then you need to place your pages [1]
[2]
[3]
[4]
in the following order: [4|1]
, then [2|3]
.