The short answer is that Linux is a computer operating system. You can use for almost anything you can imagine a computer can be made to do.
It is not Windows and doesn't work like Windows (for example, programs written for Windows will not run natively in Linux), but, with a very few exceptions (mostly some games and some highly specialized applications such as CAD programs, you can easily find Linux applications that perform equally well or better, but they might look and feel a little different.
Here are three sources I found useful when I was starting with Linux:
. It's oriented to Ubuntu, but it's full of good info.
. Machtelt Garrels's Intro to Linux.
. Slackware oriented, but excellent on the basics, such as file structure, permissions, and the like.
You can find lots of tutorials on YouTube.