What is trapping? Trapping is the intentional overlap of touching colors in your printed job.

Below is an example of what a job might look like without and with trap.

The "A" has trap, notice no white space, the light blue is "Choking" or running under the darker blue.

The "C" does not have trap, notice the white space around the "C".

The "G" is being overprinted, the light blue has been printed underneath the dark blue "G" this will change the color of the "G" where the lighter blue is under (some dark colors printing on lighter colors can overprint without a color shift, or can give the illusion of a 3rd color on a two color job.

The general rule of trapping is to spread lighter areas into darker areas. In doing so, the integrity of the darker image is maintained while the lighter color underprints.
Keep in mind that this is a generalization of trapping and at Advanced Color Graphics the combination of our Technicians and a digital workflow takes care of all your trapping concerns.