When editing a contact, you may chose to change the account that has friended the user, XMPP name, edit a roster name (which will be shown on your roster). Here, you may also decide to selectively approve or deny subscription requests to and from the user. If you do not send presence updates, they will not know whether you are online, busy, or away. If you elect not to receive presence updates, you will not receive information if they are online, busy or away.
