Profile Status
You must be "Searchable" for other members to discover your profile or see your "Online" status. Select "Hidden" to stop your profile from appearing in other members' search results. However, people you have previously communicated with will be able to view your profile.
Online Status
You can set yourself as "Offline" for the length of your session so that other members will not know you are online. You will be "Online" again the next time you login.