Bleed
Extra art running past the cut line so a slightly-off trim still lands in your design instead of leaving a white sliver.
See it
What it is
Bleed is artwork you deliberately extend past the cut line, usually 3mm (0.125in) on every side, so the guillotine has room to wander. Paper shifts a hair in a stacked pile, and without bleed that drift leaves a thin white hairline down one edge of two hundred flyers.
Anything meant to touch the paper edge (background color, photo, full-width band) has to run into the bleed zone. Set it in document setup at the start, not by nudging objects around at export time, and turn on 'use document bleed settings' when you export the PDF. Bleed is the outer counterpart to the safe area: art goes out, text stays in.
Gotcha: bleed is not a border you draw. Do not add a white frame around the design and call it bleed, and do not scale a finished flat layout up by 3% to fake it, because that shoves everything off center. A JPEG supplied at exact trim size has nothing left to extend, so ask for the source oversize before you build around it.
Ask AI for it
Set this artwork up as a print-ready layout with bleed: document size = final trim size, plus 3mm (0.125in) bleed on all four sides. Extend every background, photo, and color band fully into the bleed so nothing stops at the trim line, keep all text and logos at least 5mm inside the trim, and export a PDF with document bleed included. Follow the printer's PDF specification for printer marks: add crop marks only if they ask for them, at the offset they specify, sitting outside the bleed area rather than touching it.