There are a number of options available to Account Administrators via the drop down menu.
Reset Password - Send an email to the user with a link to reset their password. Can be useful if they are having problems using the "Forgot my password" feature on the application.
Unlock User - A user is locked after too many failed attempts. Currently there is no indication a user is locked. With the next update, a red lock icon will be shown beside the username if the account is locked.
Manually Reset Password - This can be used for shared accounts, for example where an account is being used by multiple users and no-one can access the account email inbox.
Disable Account - This prevents the user from logging in. It is a temporary measure that can be reversed by the Account Administrator.
Delete Account - This deletes the account and can also be reversed by the Account Administrator.