Glossary
Bleed
Bleed is extra artwork extended past the finished edge of a product so that small cutting variations do not leave an unprinted white sliver. Anything meant to reach the edge has to extend beyond it.
Trimming and garment placement are never exact to the millimetre. Bleed absorbs that tolerance. Without it, a design intended to run to the edge will sometimes show a thin white line on one side.
The matching idea is the safe area: keep text and anything you cannot afford to lose well inside the trim line, because the same tolerance that eats a white edge can also clip a letter.