In our Layout class, we learned about trapping. There are 10 different ways for trapping. They are Rich v Black, Patial Overlap, Obcvious Trap, Misregistration, Trapping Not Necessary, Spread v Choke, Knockout v Overprint, Third Color results through Overprinting, Knocking Our small text v Overprinting small text, and lastly Spread v Choke on small text with high contrast.
Trapping is when you add a stroke to your object, then convert the stroke into a path: Object> Path> Outline Stroke. Then fill the outlined stroke with a mix of the two colors needing trapping. Then use the pathfinder to subtract from the shape of your stoke.
Misregesistration is through the printing process, paper can shift from one color unit to the next. Without proper, or any trapping, image shifting or misregistration will results.
There 8 other ways for trapping but two were described.