What is Effect -> Pathfinder -> Trap for?

Question

Adobe Illustrator

Answer 1

Last time they already answered that this is for trapping (and in the trapping characteristics window, but personally I always did without this panel). The need for trapping, as well as its characteristics, depend on the specific type of printing. You can read more, for example, in the Adobe help (which is googled for pathfinder trap illustrator ).
Here are some more links about trapping
https://ru.wikipedia.org/wiki/%D0%A2%D1%80%D0%B5%D ...
minixpress.ru/trapping.php
settings. Explaining them without theory is pointless.