OS X Yosemite: Login Options pane of Users & Groups preferences

Automatic login

Choose Off to require users to log in whenever the Mac restarts.

To automatically log in a particular user when the Mac restarts, choose the user’s account name and enter his or her password. This option is useful if the Mac has only one user and is always in a secure location. If security is a concern, automatic login should be off. When FileVault is enabled, automatic login is disabled.

Display login window as

To let users choose from a list of user names when logging in so that they don’t have to remember their user names, select “List of users.”

To require users to enter both user name and password when logging in, select “Name and password.”

Show the Sleep, Restart, and Shut Down buttons

Show these buttons in the login window.

Show Input menu in login window

Let users choose the language OS X will use after login.

Show password hints

Display a password hint in the login window. The hint is shown during login if the user clicks the question mark in the password field or enters a password incorrectly three times in a row.

Show fast user switching menu as

Enable switching quickly between users from the menu bar. Choose how users are displayed in the menu bar from the pop-up menu.

Use VoiceOver in the login window

Allow VoiceOver to be used during login.

Allow network users to log in at login window

Let users log in to your Mac using accounts on a network account server that your Mac is joined to.

Network Account Server

To join (or connect) your Mac to a network account server, click the Join or Edit button. The button is labeled Join if your Mac isn’t connected to a network account server. It’s labeled Edit if your Mac has an existing connection.

Add and Remove

To add a new user or group, click Add , then enter the information for the new user or group. To delete a user or group, select it in the list, then click Remove .

Lock

Locks or unlocks Security & Privacy preferences. Click the lock icon to unlock it, then enter an administrator name and password.