This flip-flop toggles (Q changes state) on the negative going edge of the clock pulse.
T acts as an ENABLE / INHIBIT control.
Q will only toggle on the negative edge of the clock pulse, when T is high.
Below is shown a D type flip-flop connected as a toggle type.
On each clock pulse positive going edge, Q will go to the state bar Q was before the clock pulse arrived.
Remember that bar Q is the opposite level to Q.
Therefore Q will toggle.