What is the use of a thruster?

Excuse me, could you please elaborate on the purpose and usage of a thruster? I understand it has something to do with propelling objects, but I'm interested in learning more about its specific applications and how it functions in various scenarios. Perhaps you could explain the different types of thrusters, the principles behind their operation, and some real-world examples where they are used? I'm particularly intrigued by the potential applications in the aerospace and marine industries.