Bash (Bourne-Again SHell) is a Linux and Unix-like system shell or command language interpreter. It is a default shell on many operating systems including Linux and Apple MacOS X. Shell scripts are a fundamental part of the Unix programming environment.
If you have always used a graphic user interface like KDE or Gnome or MS-Windows or Apple OS X, you are likely to find bash shell confusing. If you spend some time with the bash shell prompt and it will be difficult for you to go back.
Here are a list of tutorials and helpful resources to help you learn bash scripting and bash shell itself. You should read the following documents if you are interested in learning the basics of shell scripting.