voluntary
Done by your own choice, not because you must.
Voluntary means done by choice rather than by force or requirement. When something is voluntary, you're free to do it or not do it. Nobody is making you.
A voluntary action comes from your own decision. If you volunteer to help clean up after a school event, that's voluntary: you chose to help even though you didn't have to. When a library offers voluntary reading programs during summer vacation, students can join if they want, but nobody gets in trouble for skipping them.
The opposite of voluntary is mandatory or compulsory, which means required. Attending school until a certain age is mandatory, not voluntary. But joining the school chess club? That's voluntary.
Sometimes people make voluntary contributions or donations, giving money to causes they care about without being forced. A voluntary organization is one where people choose to participate and work together for a common goal, like a community garden or youth sports league.
When something is voluntary, your will is free. You're the one deciding. That freedom to choose makes voluntary actions meaningful: when you do something voluntarily, it shows what you truly care about, not just what you're told to do.