Flip-Flops are used to store state information in a circuit. There are two different types of Flip-Flops which are D Flip-Flops and JK Flip-Flops. Both of these are used to store information and create two different outputs, Q and Q'. Also a clock is connected to a Flip-Flop in order for the circuit to run.
A D Flip-Flop is one that only has one input and creates two outputs. At the bottom and the top of the Flip-Flop is clear and preset which are usually connected to power. There are also two different types of D Flip-Flops, Positive and Negative Edge Trigger which change the value of the clock.
A JK Flip-Flop is one that has TWO inputs and two outputs. This type of Flip-Flop also has a preset and clear that is usually connected to power. There are also two different types of JK Flip-Flops, Positive and Negative Edge Trigger which change the value of the clock.