Both are basically the same, except the free software movement puts more emphasis on the freedom to modify and redistribute the code. For example, GNU GPL would be more "free" than MIT licence, because MIT license does not enforce copyleft and thus someone can develop closed-source software based on the code.
The essential difference, slightly oversimplified, is that Free Software generally requires that, if you modify and/or incorporate it into another body of work, the entire result must also be distributed as Free Software, and you are forbidden to further restrict the ability of any "downstream" users from modifying, using, or redistributing the software with the same rights that were given to you.
Hope that helps.







