GC - Steps

In simple words, GC works in two simple steps known as Mark and Sweep:

Mark - starts from the root node of your application(main), walks the object graph:
- marks objects that are reachable as live
- mark objects that are not reachable as dead
Sweep - delete unreachable objects
Compacting - compact the memory by moving around the objects and making the allocation contiguous than fragmented

GC - Advantages & Disadvantages

Advantages:

No manual memory allocation/deallocation handling because unused memory space is automatically handled by GC
No overhead of handling Dangling Pointer
Automatic Memory Leak management (GC on its own can’t guarantee the full proof solution to memory leaking, however, it takes care of a good portion of it)

Disadvantages:

Since JVM has to keep track of object reference creation/deletion, this activity requires more CPU power than the original application. It may affect the performance of requests which required large memory
Programmers have no control over the scheduling of CPU time dedicated to freeing objects that are no longer needed
Using some GC implementations might result in application stopping unpredictably
Automatized memory management will not be as efficient as the proper manual memory allocation/deallocation

Serial GC	`java` `-XX:+UseSerialGC -jar main.jar`	single-threaded gc on both young and old generation
Parallel GC	`java -XX:+UseParallelGC -jar main.jar`	multi-thread gc on young generation single-threaded on old generation
	`java` `-XX:+UseParallelOldGC -jar main.jar`	multi-threaded gc on both young and old generation
	`java` `-XX:+UseParNewGC -jar main.jar`	multi-threaded gc on young generation
CMS GC DEPRECATED	`java` `-XX:+UseConcMarkSweepGC -jar main.jar`	use CMS gc autoenables `UseParNewGC`
G1 GC	`java -XX:+UseG1GC -jar main.jar`	use G1GC
Z GC	`java` `-XX:+UseZGC -XX:+UnlockExperimentalVMOptions -jar main.jar` `java` `-XX:+UseZGC -jar main.jar`	use ZGC