This is a SIM900 GSM/GPRS Shield for Arduino UNO/MEGA/Leonardo. It support 850/900/1800/1900MHZ, so can be used all over the world. You can use it to make a phone call, send SMS or transfer your data to internet.
On the board there is a speaker socket and a microphone socket that can be used for the phone call.
This board can be compatible with Arduino Uno,Mega or Leonardo, for serial communciation there are sereral ports of arduino can be used. For RX port of SIM900, you can connect it to D1/D3 of arduino conveniently through the jumper. For TX port of SIM900, you can also connect it D0/D2/D8/D10 of arduino conveniently.