In java, garbage means unreferenced objects.
Garbage Collection is process of reclaiming the runtime unused memory automatically.The Garbage collector of JVM collects only those objects that are created by new keyword. So if you have created any object without new, you can use finalize method to perform cleanup processing (destroying remaining objects).
Advantage of Garbage Collection:
1 It makes java memory efficient because garbage collector removes the unreferenced objects from heap memory.
2 It is automatically done by the garbage collector so we don't need to make extra efforts.