alias - create names or abbreviations for commands
Alias can be used to correct our typos on shell command line. For example we can create sl command to simulate ls command:
$ alias sl=ls
Another way how to use alias is to create new customized commands:
$ alias estcon="netstat -ant | grep ESTABLISHED"
Alias can also be used for abbreviations:
$ alias ls="ls --file-type"
NOTE: to unalias your commands use unalias command.
$ unalias ls
However, creation of aliases with alias command is temporary just for current terminal session. To make alias permanent you need to consult ~/.bashrc file. To make changes pernament edit your ~/.bashrc file and add line similar to this:
alias ls="ls --file-type"