Aliases can be quite useful. Lets say you want to have users use the bird command but want !burb to work too. You can add an alias for the bird command so !burb does triggers the bird command.
You can also disable lets say the ban command entirely and only allow alias versions you make like !bean.
!alias command force
Ignore this command and only accept alias versions of it
!alias command trigger
Also recognize this alternative command for the original
!alias ban force
Now the ban command will only work via alias versions
!alias ban bean
Now bean will execute the ban command
Displays current aliases
!unalias command force
No longer ignores the original command accepting only Aliases
Removes bean as an alias for ban
Removes all aliases for the ban command