BBM allows users to chat one-on-one or in groups as large as 30 people. Eventually, BlackBerry will add Video Calling and Voice Calling to the app. Unlike other messaging apps that use a username or email address, users are given a PIN number which they use to initiate or accept conversations.
BlackBerry is moving BBM Channels from the Beta Zone to the BlackBerry App World later today. This feature will eventually be added to the Android version of BBM and allows members to join communities filled with people having the same interests. The iOS version of BBM will receive all of the same updates that Android users are expected to receive.
source: BlackBerry via Crackberry