Aliases are redefinitions of commands, usually in shortened form. Systemwide alias definitions are entered by the root operator in the bashrc file under the /etc directory, but you can define your own in your .bashrc file. Several of these aliases are especially useful:
alias cp='cp -i' alias mv='mv -i' alias rm='rm -i' alias ls='ls --color=auto'
In this example you are redefining the default action of the cp, mv, and rm commands to use interactive querying, which provides a measure of safety when copying, deleting, moving, or renaming files. Aliases can also be used to craft new commands or variations of often-used commands and command-line options, such as redefining ls to use color by default.
In a more detailed example you ...