In automotive terms, a rim is a type of open wheel of a one-piece design, usually with spokes radiating from a central hub. If you can see the brake calipers through the wheels, you're looking at rims.

Rims are most often found on sports and luxury cars, modified Hondas and the like.

Various trim levels of the same car model are often differentiated by rims with a certain number of spokes. For example, a sport model might have six-spoke rims while the base model has five spokes.

This usage could probably be considered slang, as I hear it most frequently among young car addicts. Technically, the rim is also the outside edge of any wheel, where the wheel meets the tire.