It just so happened that just when Linux was getting usable, GNU had everything it needed except a kernel. Thus, people started using Linuxwith GNU to make a completely free UNIX-like operating system called GNU/Linux.
Freesoftware does NOT mean that you do not have to pay to get it. Freesoftware is a matter of freedom, not price. In order for software to be free, users must be able to run, copy, distribute (with a fee or without a fee), study, change and improve the software.
A copyleft free software license. That means that anyone can do anything withsomething under the GPL except deny others' rights given by them by the GPL. Also the GPL requires that all copyright notices and notices that refer to the GPL stay.
What all computers were beforeGUIs came about. CLI is an interface that only uses text. Some stupid people and groups (like micro$oft, apple and linspire) try to get rid of CLI taking a lot of poweraway from users. CLI is still used a lot on UNIX and UNIX-like OSs.