Sexual abstinence is when someone decides not be sexually active. Being abstinent is a conscious decision that one makes and you can make it at any point in your life. You can make the decision in your teens, 20's, 30's, 40's, 50's, and so on. People have all sorts of different reasons to choose to be abstinent.
For whatever reason you're being abstinent for whatever personal reasons you have, you want to make sure that you come to that decision on your own. It shouldn't be your partners decision whether or not you choose to be sexually active.
There are many benefits to not being sexually active such as preventing pregnancy, preventing infections such as STD's. These infections are when one person passes an infection to their partner such as a-nal sex, vaginal sex, and oral sex.
Some other benefits com down to people's own personal opinions such as waiting to find the right partner and focusing on more important activities in someone's lifetime before making this decision.