Free Software / Open Source Software
The terms Free Software and Open Source Software essentially mean the same thing: Software the source code of which is made public so everybody can read and even modify it.
For several years now, I have been using (GNU-) Linux systems. Only on old and special hardware (for which there are no Linux drivers), I am still using Windows. Apple hardware has never been an option, as Apple tries to lock users in.
I have tried other Unix derivatives as well, but I found that at least for me, Linux works best.