Many people find that the sensation of having their ass or vagina completely filled and stretched out is a fantastic one. Fisting is pretty much what it sounds like: getting your entire hand inside someone and fucking them with it as long as they can handle. It does take practice, however, and you should be extremely careful not to hurt or damage your partner as you figure things out. Time, patience and lubricant are all essential, as is a relaxed partner who feels comfortable and is massively turned on. Many people find that having an orgasm before playing around with fisting makes things a little more straightforward, making that the perfect time to start finding out if it's for you.