Short answer: Plumbing repair covers fixing the specific failed part of a pipe, faucet, toilet, garbage disposal, or water heater rather than replacing the whole thing.
A repair fixes what's actually broken — a worn cartridge, a failed seal, a cracked section of pipe — without replacing an entire fixture that's otherwise in good shape. It's usually the first thing worth considering before jumping to replacement.
The pages below break repair down by what's failing, since a leaking pipe, a running toilet, and a water heater problem all call for different diagnostic steps.