Sertainly no directfire weapon, basicaly it was a SdKfz-251 halftrack whit an 81mm mortar on the floor and ammunition boxes. The mortar could be fired from the vehicle or taken out and fired normaly from the ground. Only reason for halftrack mounting was that it could keep up whit the mechanised infantry and provide fast fire support.
Picture of the 81mm mortar on the halftrack floor:
