.Net has 3 Generations of garbage collection.

Generation 0:- garbage collector runs most often on this generation of defined memory heap. During garbage collection, If any object has no reference, then it clears that memory or else pushes that memory to Generation 1 category.

Generation 1:- Here garbage collector visits those heap memory comparatively less frequent with respect to Generation 0.

Generation 2:- Frequency of garbage collection is very less as those memory heaps keeps an active object reference. For example static class, variables memory reference falls under this generation.