utility (for ``superuser'') can be used to
switch over to another account temporarily. It is primarily
used to access the root account, when it is executed
without an argument. Otherwise, it is used in this form:
su prompts for the account password, and if it is correct, a Bourne shell is started under the other account. Transitions with su do not affect the login user ID (LUID), so login and audit records remain accurate.
If a dash (-) is present on the command (su -), the environment for that user is executed (including login shell and home directory), making it essentially the same as logging in as that user. To exit the shell, enter exit or press <Ctrl>D and you return to your own account.