lists your current aliases
alias erase command
removes "command" from your alias list
alias add command [what-to-do]
adds "command" to your alias list.
"command foo" afterwards will be the same as typing "what to do foo"
If you want to place the arguments in the middle instead of after the text the alias expands to, use $*. For example if you do 'alias fish say $* bang' then do
'fish foo', then it will make you say 'foo bang'.