The outputs of a basic SR flip-flop change whenever its R or S inputs change appropriately. A clocked SR flip-flop has an extra clock input which enables or disables the other two inputs. When they are disabled the outputs remain constant.
If we connect two clocked SR flip-flops so that the Q and /Q outputs of the first, "master" flip-flop drive the S and R inputs of the second, "slave" flip-flop, and we drive the slave's clock input with an inverted version of the master's clock, then we have an edge-triggered RS flip-flop. The external R and S inputs of this device are latched on one edge (transition) of the clock (e.g. the falling edge) and the outputs will only change on the next opposite (rising) edge.