In Short

Twitter is a "microblogging" social network that allows users to send short status updates that consist of up to 140 characters. Twitter was originally designed to work over SMS, so users could opt in to receiving Tweets from specific individuals. Official apps from Twitter are available for BlackBerry smartphones that allow users to send Tweets, upload photos, view their timeline, share location, and more. Twitter is integrated deeply into BlackBerry 10 so users can send and receive private direct messages in the BlackBerry Hub. 

Twitter is a great resource as a multi-platform messaging tool, news service and much more. In addition to the official client, currently there are a handful of third-party Twitter apps available for BlackBerry like Blaq, Twittly and more!