A very special connection within the flip-flop is the feedback path from the output of one NAND gate into the input of other gate. This characteristic feedback determines the truth table of the flip-flop as well as its memory property.
For instance, let us assume that S = 1, R = 1, Q = 0 and = 1 initially. If S goes low, the output of NAND gate 1 goes high. Both inputs of gate 2 are high so that  = 0. This low signal is fed back to an input of gate 1 and keeps Q = 1 even if S =1 again. For the same reason, further change of S to 0 produce no effect.