Java garbage collection is an automated process that deletes code no longer needed or used, freeing up memory space and making coding easier for developers. It occurs most frequently in the young generation (eden and survivor spaces) due to many new objects being short-lived, but can also occur in the old generation (tenured space) where long-lived objects are stored. The garbage collection process uses a mark-and-sweep algorithm, which scans different parts of the heap looking for unused objects and removes them to free up memory. While automatic garbage collection offers several benefits such as preventing memory leaks and increasing productivity, it can also lead to performance issues if not optimized properly. Developers can optimize garbage collection by choosing the right collector, monitoring logs, optimizing heap size, tuning parameters, minimizing object creation, and using parallelism and concurrency. Monitoring Java application performance with tools like New Relic can help detect and triage issues related to garbage collection and improve overall performance.