Instant messaging makes it possible for users to communicate with each other in real time on their computers using text-based messages. Basic IM is the exchange of text messages between two users. Users can invite additional people to an IM session. When an additional contact is added to the IM session, the session becomes a conference, and the behavior of the conversation window changes to support conferencing features.

Presence provides information to users about the status of other users in their contact list. A user’s presence status provides information to help others decide whether they should try to contact the user and whether to use instant messaging, phone, or e-mail. Presence encourages instant communication when possible, but it also provides information about whether a user is in a meeting or out of the office, indicating that instant communication is not possible. This presence status is exposed as a presence icon in Office Communicator 2007 R2 and other presence-aware applications in the Microsoft Office 2007 system, including the Outlook messaging and collaboration client, SharePoint technologies, Word, and Excel. The presence icon represents the user’s current availability and willingness to communicate.