Hi. I'm a 13 (almost 14) year old male and I'm wondering: What is masturbation? And how can you do it if it's heathly?
Masturbation is touching and playing with your genitals to get yourself sexually excited enough that you end up ejaculating semen. While some boys do play with their privates even when they are young, you will not be able to ejaculate until your body is developed enough to produce semen. Typically the ability to ejaculate comes sometime during stage 3 of development; the same phase when you have your rapid growth spurt.
There is no particular reason to pursue masturbation. Once your body gains the ability to produce semen, it will get rid of excess semen periodically through wet dreams. So masturbating is not going to make you more or less healthy. Some boys use masturbation to avoid wet dreams. Others are bothered by the strong sexual urges that arise as the seminal vesicles begin to get full, so they cause themselves to ejaculate to lower the urges. Most discover it accidentally and continue to masturbate simply because it feels good.
The later reason is the most dangerous because it is easy for a teenage boy to become obsessed with the sexual pleasure. It becomes a lust for them and Satan can use it to tempt them to sin just to get that feeling another time. That is why a lot of boys get trapped into sinful behavior, such as looking at pornography or toying with fornication or homosexuality.
How do I know when my body has developed enough semen? Can you "force on" wet dreams?
Being able to ejaculate is one of those things which is very hard to miss. No, you can't force a wet dream. It comes because your seminal vesicles are too full and can't hold much more semen. This sets up a series of events which leads to a wet dream, through which your body gets rid of the excess semen. Besides the weird dream, you will know that it has happened because you will find a sticky white liquid in your pajama bottoms or on your bed sheets (if you wake up during or shortly after the wet dream) or a stiff stain (if you sleep the rest of the night and it dries by morning).
Another way boys find out they have reach the point of being able to ejaculate semen is when they are showering or touching their genitals (often without much thought) and along with an erection their penis squirts out a whitish liquid, which is semen. The feelings that come with this are strange and hard to describe, but like I said, they are hard to miss.