T memory cells and B memory cells are two types of cells involved in immunological memory. Both are part of the adaptive immune system. 

The main function of both is to generate secondary immune reactions. Both, T memory cells and B memory cells, have the ability to memorize the characteristics of antigens that activate their naïve counterparts. On encountering the same antigen at a later time, both memory cells recognize the antigen and mount an accelerated and robust secondary immune response.