Classifications yards are arrangements of tracks used to sort or classify cars. They recieve inbound trains or cuts of cars, switch them according to their outbound blocks and then build them into outbound trains.
Large yards may have subyards separated by function.
Arrival/Departure yard/tracks: Longer tracks designed to recieve and inbound train or cut or tracks in which an outbound is built. Large yards may have separate Arrival and Departure yards.
Classification yard/tracks: Shorter tracks used to sort or classify cars by outbound block.
City yard: small yard used to hold local industry cars.
RIP tracks: Tracks where cars are repaired (Repair In Place).
Caboose tracks: Tracks used to hold cabooses between trains, where they can be cleaned and serviced (fuel, ice, water, supplies, etc)
Switching lead: track dedicated for use by the switch engine while classifying cars. Gives the switcher tail room (room to pull back)while switching.
Scale track: track with a scale on it to weigh cars for billing purposes.