A weed trimmer is made up of a motor, a trimming head, and a shaft that often contains electrical wires and is attached to the handle. A monofilament line, similar to fishing line, does the actual trimming.
The placement of the motor depends on whether it is a gas- or electric-powered weed trimmer. Electric-powered motors are usually at the bottom of the shaft near the trimming head, while gas-powered motors are often at the opposite end of the shaft. The monofilamnt line wraps around the trimming head with loose ends extending out from the head, which causes the line to spin rapidly enough to cut grass and weeds.