The command line is the most powerful part of the operating system. It allows you to manipulate almost every aspect of the operating system. Mastery of the command line is essential to being a true expert in Linux.
Linux and other Unix-like operating systems can use different shells or command lines, with differing advantages and disadvantages. Here are some of your choices:
1. Bash - Bourne Again Shell is one of the most widely utilizes shells for its simplicity and ease of use. This is more commonly used in Ubuntu and other Debian based OSes.
2. Csh - C shell is a shell which is more similar to the C programming language. It is used in Macs and BSD based systems.
3. Tcsh - An improved version of C shell, It is more programmable and has a wider feature range than Csh.
4. Zsh - The Z Shell is a powerful command interpreter which can emulate other shells, like bash or csh. This makes this shell very customizable.
5. Korn shell - This is one of the newest shells available, and is considered an improvement over Bash.