Below is an excerpt from a good explanation of the <a href=”http://dept-info.labri.fr/~strandh/Teaching/AMP/Common/Strandh-Tutorial/flip-flops.html”>difference between a latch and a flip-flop</a> .
In the same way that gates are the building blocks of combinatorial circuits, latches and flip-flops are the building blocks of sequential circuits.
While gates had to be built directly from transistors, latches can be built from gates, and flip-flops can be built from latches. This fact will make it somewhat easier to understand latches and flip-flops.
Both latches and flip-flops are circuit elements whose output depends not only on the current inputs, but also on previous inputs and outputs. The difference between a latch and a flip-flop is that a latch does not have a clock signal, whereas a flip-flop always does.