The capacity for people to have the freedom to choose between different possible courses of action without influences like coercion.
For instance, humans live how they want; I live how I want. Free will is doing things on purpose, and suggests that one's own self has a stake in decision-making. But do they really?
I used to believe in free will. But on second thought, I think it was optimism bias. After all, everything is likely "determined" by the brain and space-time, and the illusion may be just that we don't understand the brain fully; however, of course, it inevitably converges to a single path. Is it even free now?
For an argument, see Determinism