When the two inputs J and K are connected together, a T flip flop or a Toggle flip flop is formed. This type of flip flop has only one data input T. It has to be either edge triggered or Master/Slave Type.
Let Qn and Qn+1 represent the present and next state of filp flop, here is the truth table and circuit diagram of a T Flip Flop:
When the input T is a t 0 level prior to a clock pulse, the Q output will not change with clocking. When the input T is at a 1 level, the Q output will in the Qn’ state after clocking i.e. Qn+1=Qn’. Thus the output will toggle.