Parts cut on a laser are generally made with a tolerance of 0.005 inches (5/1000 of an inch). This means that you should not depend upon features to be more accurately placed than 0.005 inches. Holes may be up to 0.01 inches smaller or larger than your specification.
Kerf is the cutting width of the tool used to make your parts. We typically cut parts with a laser beam width of 0.01 inches. Features smaller than this size may be lost. Also, inside corners have to be able to accommodate the width of the laser beam.
Melting of plastic materials of charring of wood may also affect accuracy.
Parts will have a slight taper along the cut edge of the part, typically approximately 0.01 inches.
Laser cutting plastics produces a fairly smooth surface, particularly when compared with waterjet cutting. Here is what 0.118 inch thick clear acrylic plastic looks like after being cut with a laser:
A closeup of the above image:
Your part may have a small tab where the part was held to the stock material. You can remove this tab with a file or a similar tool.