Definition of Microblogging (according to Wikipedia (en)):
Microblogging is a broadcast medium that exists in the form of blogging. A microblog differs from a traditional blog in that its content is typically smaller in both actual and aggregated file size. Microblogs "allow users to exchange small elements of content such as short sentences, individual images, or video links", which may be the major reason for their popularity. These small messages are sometimes called microposts.
As with traditional blogging, microbloggers post about topics ranging from the simple, such as "what I'm doing right now," to the thematic, such as "sports cars." Commercial microblogs also exist to promote websites, services and products, and to promote collaboration within an organization.