"Free software" refers to freedom, not price. It means that the user has four essential freedoms:
Freedom 0 is the freedom to run the program as you wish.
Freedom 1 is the freedom to study the source code and change it to do what you wish
Freedom 2 is the freedom to help your neighbour. That's the freedom to make copies and distribute them to others: to give them away or sell them.
Freedom 3 is the freedom to help your community. That's the freedom to distribute modified versions, so that everybody can benefit from your contribution.
With all 4 of these essential freedoms, a program is a free software. That means that it is distributed in an ethical way, a way that respects everyone's freedom.
Then idea of a free software movement is that every software user should always have these freedom; no one should ever take these freedoms away from you.