Bleed refers to an extra 1/8" (.125 in) of image or background color that extends beyond the trim area (final size) of your project. Bleed gives the printer a small amount of leeway to account for natural movement of the paper during trimming. The project is printed on an oversize sheet that is then cut down to size with the appearance that the image is "bleeding" off the edge of the paper.
If images or colors bleed, be sure to include 1/8" bleed on all sides. For example, a full bleed business card would be 2.25" x 3.75". Also, be cautious of the "Safe Zone" on any project involving cutting. Make sure any text or other item you don't want to have cut is at least 1/8" in from the trim line.
If your file does not have bleed, and cutting isn't indicated, Document Services will scale your file to fit whatever stock you choose, and there will be a white border around the print.