Linux is a free version of UNIX (or UN*X). The free part is not meat in money terms but rather that the source code for Linux is freely available for inspection, modification and what you feel you can/should do...
Linux is a multitask and multiuser operating system. Now, a little explanation of this terminology.
An operating system is a collection of programs that run in a computer so that a person can easily access the hardware and all resources of the computers. The operating system is the big program that makes your computer life easy (or difficult, it the operating system is a bad one).
A multitask operating system is capable of doing several tasks at the same time (well, not quite so, but it seems like that from the human point of view).
A multiuser operating sytem has a concept
of "userquot;, a way to identify the person that is using the
system, and can allow different users to perform different taks in the
computer, and protect one user's tasks from interfering with another
User Name and Password
So, when you want to work in a computer running Linux the first thing
you need is a user name (or logging name). That will be given to
you by the person that administrates the system.
You will also need a password to be sure that only you use your account. An initial password might be given to you by the system administrator; you can change it later to something that you can easily remember. But try some password that is difficult to guess, or any one will be able to use your account (and remove your files, send email on your name, etc).
There are a few other terms that will help you to understand the rest of the this manual: