When AT&T software engineers Dennis Ritchie and Ken Thompson were designing UNIX™, they wanted to create a way for people to interact with their new system.
Operating systems at that time came with command interpreters, which could take commands from the user and interpret them so that computers could use them.
But Ritchie and Thompson wanted something more, something that offered better features than the command interpreters available at that time. This lead to the development of the Bourne shell (known as sh), created by S.R. Bourne. Since the creation of the Bourne shell, other shells have been developed, such as the C shell (csh) and the Korn shell (ksh).
When the Free Software Foundation sought a royalty-free shell, developers began to work on the language behind the Bourne shell as well as some of the popular features from other shells available at the time.
The result was the Bourne Again Shell, or bash. Although your Red Hat Linux system includes several different shells, bash is the default shell for interactive users. You can learn more about bash by reading the bash man page (type man bash at a shell prompt).