Spare parts can be many different things and belong to many different things. You can talk about classic parts for all motorized vehicles, such as cars, tractors, motorcycles, etc., but you can also talk about electronics, such as. Computer and camera, as well as various other machines.
Some spare parts can be very rare. It may be that you have a car from the 60s and something about this needs to be replaced, but as you want the original parts, it can be difficult. Fortunately, some people are all about looking for special classic parts, and they can even replace them.