Aliases can help in issuing complex or long commands by creating short aliases for them.
Aliases can be created for the session or persistent ones by adding them to .profile or .bashrc file depending on what flavor of Unix you are using.
Example:
alias l=’l -al’#this will create alias for list command with couple of paramter
alias alert=’cd /u02/diag/rdbms/prod/prod1/trace’ #this creates alias for alert log location for oracle