See also:
What is a mathematical description of free will?
Is free will reconcilable with a purely physical world?
What is the difference between free-will and randomness and or non-determinism?
The world is either deterministic of non-deterministic.
In the case of determinism, all of the actions are predetermined, so one cannot really choose one's actions. In the case of non-determinism, actions are also determined by some randomness and this randomness is a true randomness, not something that's depending on a hidden mechanism of any kind.
It is often argued that non-determinism allows for a free will. However, the randomness it contains, that would give a place for a free will, is a true randomness, so it isn't being chosen by anybody, it's just purely random.
From that perspective, it appears that "free will" is an ill-defined concept. Are there any better (more useful) definitions?