Junkyards usually specialize in one type of vehicle - most often cars. They will pay car owners for old vehicles - often cars so old or beaten up that they aren't worth fixing. If the car is undrivable, the junkyard may pick it up at the customer's house. In that case, the customer may pay the junkyard to tow the car off. Junkyards also sometimes buy cars from police auctions.
Junkyards have huge numbers of cars in varying states of decay. They will inventory the usable parts of each car and record where it is located in the junkyard. To save space, they will sometimes use cranes to stack them on top of each other or on large metal racks. Other junk yards will remove particularly valuable parts and store them in a warehouse. This will stop the parts from decaying from the effects of weather.
Junkyards make money in a variety of ways. They will sell parts to individual customers, who are usually responsible for installing the part themselves. In some junkyards, the customer has to remove the part while in other ones, the yard removes the part for him. Junkyards also sell larger parts such as engines to used auto part companies, which repair them and sell them to car builders and garages. Junkyards also sell unusable parts to to scrap metal recycling companies. A large enough junkyard can sometimes perform some other tasks. For example, a big junkyard might also reassemble and sell engines.