Lighting contactors are similar to a relay, but they are meant to handle higher currents and larger loads. They are commonly used in industrial or commercial applications.
Contactors are made to last for several years under these large loads. They have two basic parts, the coil and the contacts. If one fails shortly after installation it can sometimes be a simple fix such as replacing the contacts if they are pitted or corroded. The coil can replaced as well. Normally, failures of these types are caused by overheating or an improper load on the circuit itself. Replacing these parts can be much simpler than trying replace the entire unit.