The T flip-flop, or toggle flip-flop, can be created by connecting both inputs on a JK flip-flop to the same source. This type of flip-flop can be used as a frequency divider. The T flip-flop will toggle the output on each clock cycle when both J and K inputs are high, so the output frequency will be half of the input frequency.
The filter and edge detector can be used to filter out any spikes that would cause the JK to toggle unintentionally.