RedHat/Linux

Open source
Generally, open source refers to a program in which the source code is available to the general public for use and/or modification from its original design. Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community. Open source sprouted in the technological community as a response to proprietary software owned by corporations.

Linux Distributions
A Linux distribution is a member of the family of Unix-like operating systems built on top of the Linux kernel.

RHEL
Red Hat Enterprise Linux is a Operating system developed by red hat targeted towards the commercial market, is available in server versions.


Command Line Interface (CLI)
Most computer users today are only familiar with the Graphical User Interface (GUI). A command-line interface (CLI) is a means of interacting with a computer program where the user issues commands to the program in the form of successive lines of text (command lines).

The Shell
When we speak of the command line, we are really referring to the shell. The shell is a program that takes keyboard commands and passes them to the operating system to carry out. Almost all Linux distributions supply a shell program from the GNU Project called bash. The name “bash” is an acronym for “Bourne Again SHell”, a reference to the fact bash is an enhanced replacement for sh, the original Unix shell program written by Steve Bourne.