Trailer hitches come in two main configurations: receiver type and fixed-drawbar type. Receiver-type hitches consist of a portion that mounts to the frame of the vehicle that has a rearward-facing opening that accepts removable ball mounts, hitch bike racks, cargo carriers, or other hitch mounted accessories. Fixed-drawbar hitches are typically built as one piece, have an integrated hole for the trailer ball, and are generally not compatible with aftermarket hitch accessories.
A trailer hitch typically bolts to the chassis of the vehicle. In North America there are a few common classes: I, II, III, IV that are defined by the SAE. Some manufacturers market Class V hitches, but there is no such thing according to SAE J684.
Class I —up to 2,000 pounds (910 kg) — light loads
Class II —up to 3,500 pounds (1,600 kg) — light loads
Class III —up to 5,000 pounds (2,300 kg) — larger loads (campers, boats, etc.)
Class IV —up to 10,000 pounds (4,500 kg) — larger loads (campers, boats, etc.)