A cam is a simple woven design around a bath towel, hand towel, or wash cloth usually not at the edge of the towel, but an inch to two inches (2.54-5.08 cm) in from the edge. While you can feel the loops on most towels made of terrycloth, the cam border is flat, providing a different texture and interest to the towel. This is achieved by applying a different weave to the border, to produce a flat, non-terry looped look.
The cam border is less decorative that towels with a dobby border. The dobby border features patterns or designs woven into the flat, separate weave portion. The cam border, conversely, is just a straight line across, generally less than an inch thick, with no specific patterns or designs were there are no terry loops. Some people prefer cam borders to dobby borders since it is a simple design and are less expensive.
The standard towel desgin with a cam border usually has two borders, one near the top, and one near the bottom edge of the towel. This is the same for towels with dobby borders. There are also towels with no cam or no dobby borders and are just terry loops on the entire towel.