CD4027 is a common JK Flip flop based IC and if often used as data storing element. It contains two identical or symmetrical JK flip flop. Individual set of flip flop has provision of pin like set, reset, clock input, J, K and complementary outputs. JK flip flop can be used in applications like registers, counters or as control circuits.
A small clock pulse will given to the input of IC as soon as you press the switch as a result of it pin 1 output became high. Till the second pulse will receive the output remain high. Load or Led attached with output activates. When the second clock pulse reaches on pin3 IC output turn low and LED or load attached to it become off.