Makes the orgasm more intense but gives you a headache afterwards. I only do it occasionally. Usually when I'm getting a blow job, and I'm feeling particularly dirty. You can do it without coming but it can lead to a floppy dick for a few minutes, not necessarily what you would want. Usually I cum naturally. There are some good internet sites that go into more detail, suggest you check them out. Also need to watch out if you have any health conditions.