Weighing less than 100kg, they provide GPS navigation, weather predictions, and Earth observation just like traditional satellites; but they are faster to build and much cheaper.
A typical microsatellite can cost as little as 10 million euros as opposed to hundreds of millions for traditional satellites. About 400 microsatellites have been launched in orbit over the last 20 years for scientific, commercial and military purposes.
The high maneuverability of microsats enables them to perform tricky tasks such as refueling and fixing satellites already in orbit, or correcting their trajectory to keep them on the right spot. There are about 800 satellites orbiting at the moment, whereas 66% are for communications, and 6% are in use by the military.