You may already have background in this, though for the benefit of those reading on...

There are two principle approaches to memory management. One is to keep reference counts on objects, freeing the object when the count reaches zero. It's more work up front, but memory is freed promptly. One downside is that self-referential structures never reach zero reference counts, and hence are never freed. Perl5 uses this approach.

The second scheme is to periodically sweep through memory, tracing out objects that are reachable through known starting points (e.g., global variables, stack frames), and freeing anything that isn't reachable. There's ongoing overhead, but garbage collection can take noticeable time (though there are many clever optimizations that can make this approach run quickly). Self referential structures that are not otherwise reachable do get freed. Most Java implementations use this approach.