Droids perform a variety of tasks in every climate imaginable across the galaxy. Unlike a sentient labor force, they require relatively little time to recharge, their components are easily replaced when worn out, and they can be affordably replaced when beyond repair. While some repairs may be handled by the droid's owner, many repairs require a repair droid or the expertise of a trained technician.
The parts required to repair a droid can be as varied as the droid or problem itself. Small motors, servos, gears, wires, microchips, sensors, lenses, and plating are just a few of the many different components that may be needed for a repair job. Most droid companies produce new replacement parts for their droids, but salvaged parts are also readily available at junkyards and small shops across the galaxy for the droid mechanic on a budget. You should be careful in determining if attempting a repair on your own or with used parts will invalidate any warranty your droid's manufacturer may have offered.