Garbage collector is mainly used for automatic memory management.It is used to monitor leaked and unused memory objects that are loaded into memory.garbage collector releases memory objects.If they are not in use for a longer period.

system.gc.collect() is method used to release the memory resources programatically.

Garbage collector is a process which is resides in memory and it clears memory when more space is not available on the memory it removes the objects which are not refrenced.

Memory Management a part of CLR functionality is a important aspect in .NET.

Garbage Collector well known as GC is the one responsible for Memory Management.

GC Runs periodically through Managed Heap (Which is divided into 3
Generations) and find the object which doesn't contain any reference. It then
collect those objects to free Managed Heap. After collecting the unreferenced
object GC will then Defragment Managed Heap in order to get continuous block of
memory.

GC.Collect() is a method used to call GC exclusively. However it is
recommended not to use this method often as it will promote the object left in
Heap to higher generation.