I take free will as allowing yourself to take ANY action you wish.
Mostly, when people talk about free will, they mean something like this:
Suppose you decide to raise your hand and then you raise your hand. Was that a "free" choice you made?
The usual argument against free will goes something like this: the fact that you exist at all is due to a long line of one thing causing the next thing, stretching back at least as far as the big bang. The fact that you decided to raise your hand at that particular moment can be fully explained by examining the development of your mind until your current age, the particular circumstances in which the opportunity arose for you to make the decision you made, the configuration of your neurons at the time you came to make the decision to raise your hand, and so on and so forth. Therefore, your choice to raise your hand at this moment can in no way be considered "free". Rather, your choice was determined by the laws of physics and all the interactions that led to your being here to raise your hand, your having a suitable brain to make the decision to raise it, and all the circumstances that affected your making the choice to raise your hand rather than not to raise it at this moment.
People who make this kind of argument against free will would say that the only way any choice or decision could possibly be considered "free" would be if you could somehow break the laws of physics and thus avoid all those influences that "made" you choose one thing and not another. But that's impossible, so therefore free will is impossible.
Free will does not require that you can do literally anything you want. All it requires, according to the people who make the argument just outlined, is that you can do at least
one thing that is solely a result of your choice, and which can't be put down to external factors that "compelled" you to make that choice. But, those people say,
all the choices you make are influenced or determined in one way or another; ergo, no free will.
There are a few different ways that one can attempt to refute this argument against free will. One is to deny that there is an unbroken chain of causes that can, in principle, explain any choice you make. For example, one could assert that the human will is special (possibly magical), and the consciousness, or something, is able to "break the chain of causation", to make choices truly free of "outside" influences.
Another approach is to dispute the definition of "free" that is implicit in the argument against free will. That argument says you are free only if you can somehow break the laws of physics, which is impossible. But perhaps "freedom" doesn't require that kind of magic. Maybe you're "free" as long as you are actually able to achieve what you chose to achieve. In that case, you demonstrated that your choice to raise your arm was a "free choice" when you raised your arm. You did exactly what you chose to do. Nothing stopped you acting on the choice you actually made, so it can rightly be considered a free choice. The only choices that are not free are the ones where something prevents you from achieving the desired goal - a person, an inconvenient law of physics, etc.
There are other arguments for and against free will.