Consider the circuit shown, built with NOR gates. This is a classic latch circuit. Because of its functionality it is called RS latch, where R stands for "RESET" and S for "SET".
Due to the feedback an unusual truth table is produces...
By setting up the circuit, this will become more evident to you. When connecting the battery, either Q or Q' will light up. This is determined by chance.
Suppose Q is lit, you can use the push button switch R to switch the lit LED's: Q' lits and Q extinguishes. With S you switch it all back again.
If you release both push button, the circuit stores which push button you pressed last... Either R (Q' =1, Q =0) or S (Q =1, Q' =0). Try this for some time.
To make it even clearer how latches store information, you expand the RS latch in the last experiment.