A bleed is when printing extends to the edge of the finished sheet. By default, digital printing leaves 0.25" blank margins around the edge. To print to the edge, the file must be setup in a special way so that the printers can print it slightly larger than the finish size. Printed copies are then trimmed to remove the extra print and white space, leaving you with borderless color copies. Because of the larger paper and additional finishing involved, bleed printing does add cost to the color copies. If you're trying to keep your costs as low as possible and don't mind the white borders, avoid printing with bleeds. But if your design only looks right printing to the edge, make sure your files are setup correctly and choose Bleeds: Yes, print to edge.