BlackBerry Messenger (BBM) is a proprietary Internet-based instant messenger application included on BlackBerry devices which allows messaging between BlackBerry users. It was developed by Research In Motion (RIM), maker of the BlackBerry device. Messages sent via Blackberry Messenger are sent over the Internet and use the BlackBerry PIN system, so communication is only possible between two BlackBerry devices.

The service requires the BlackBerry Internet Service to be able to function, and communicates over the phone's Internet connection using either the mobile phone network or a wireless LAN ("Wi-Fi") connected to the Internet. Thus a user can exchange messages even where there is no mobile phone network coverage provided that there is a wireless LAN accessible that allows the phone access to the Internet.

Exchanging messages is also possible via dedicated discussion or chat groups, which allow multiple BlackBerry devices to communicate in a single session. In addition to offering text-based instant messages, BlackBerry Messenger also allows users to send pictures, voicenotes (audio recordings), files, location on a map, and a wide selection of emoticons (also known as "smileys") over the Blackberry network.

With the release of BlackBerry Messenger 5.0, BlackBerry allows users to use a QR Code barcode to add each other to their respective friends lists rather than using only numeric PIN identification or an email address associated with the user's BlackBerry.

BBM was introduced Globally 15/2/08, but introduction of the new interface in April 2009 increased sales hugely.

Soure: Wikipedia