They have several representative, regulatory, administrative and developmental functions.
1)They institute solving the disputes of villagers. They do that by helding public meetings and collection the advice and opinions of everyone. (administrative function of the gram shabha.)
2) Promotion of educational, health, agriculture and communication facilities in the village. ( developmental function of gram sabha.)
3) The sarpanch, gram sevak and members represent the voice and opinion of the village people to the gram panchayat to the taluka and zillia level. (representative function of the gram sabha.)
4) They conduct regular meetings and keeps record for various departments. (regulatory function of teh gram sabha.)
hope it helps... ;)