On MACs, MacBooks, MacBook Pros, and Mac minis, etc.,
multiple user accounts can be created,
allowing users to select a certain account to log in to when powering on the computer.
If you run out of space or for other reasons, you may one day decide you want to delete one of the user accounts.
To delete a user account, you could follow these steps:
(1) Log in to the account you plan to delete
(2) log out of iTunes
(3) log out of iCloud
(4) log out of iMessage
(5) log out of the account you plan to delete
(6) log in to another user account
(7) go to System Preferences -> Users
(8) delete the account