A1 and A2 are the control contacts as mentioned above. You could have addition Terminals like AUX1 and AUX2 with are obviously auxiliary contacts with you want to control another contactor or equipment (I have seen them label A1 and A2 as well). You could go to any real electrical wholesaler (not a HD or Mom & Pop Hardware store) and the person at the desk would gladly answer your question regarding your contactor.