A simple answer that i can tell you about flip - flop is:
Flip-flops, also called bistable gates, are digital logic circuits that can be in one of two states. Flip-flops maintain their state indefinitely until an input pulse called a trigger is received. When a trigger is received, the flip-flop outputs change state according to defined rules and remain in those states until another trigger is received. Flip-flop circuits are interconnected to form the logic gates for the digital integrated circuits (IC s) used in memory chips and microprocessors. Flip-flops can be used to store one bit, or binary digit, of data.