The info is send to meteorological centers and the target is to supply a large amount of data regarding earth atmosphere, in order to help analyze and give more accurate weather prediction.
The data is send from some airplanes via sattelite or VHF stations.
It is more accurate and less expensive than the data send from meteorological baloons.
The data is send automatically. For ex ,during climb it is send at 30 sec interval ,and generally includes position ,wind and temperature. May also include humidity, iceing,..
During cruise the data is send at 15 min interval.
It may also be requested from the ground.