If you hover that button with your mouse pointer you can read the following explanation:
Send three "heap-minimize" notifications in a row. Each notification triggers a global garbage collection followed by a cycle collection, and causes the process to reduce memory usage in other ways, e.g. by flushing various caches.
Send three "heap-minimize" notifications in a row. Each notification triggers a global garbage collection followed by a cycle collection, and causes the process to reduce memory usage in other ways, e.g. by flushing various caches.