Linux is an open source operating system whose source code can be modified and customized by users to create different distributions that can run on various computers and devices. This document discusses common Linux commands like date, ls, cd, mkdir, rmdir, pwd, and echo. Date displays the system date and time. Ls lists files and directories. Cd changes the current working directory. Mdkir creates new directories. Rmdir removes empty directories. Pwd displays the present working directory. And echo displays or writes a string to a file.