Minecraft wiki entry for Memory, associated text: There are several basic categories of latches, distinguished by how they are controlled. For all types, the input lines are labeled according to their purpose (Set, Reset, Toggle, Data, Clock). There are also more arbitrary labels: The output is commonly labeled Q for historical reasons. Sometimes there is also an "inverse output" Q̅, which is always ON when Q is OFF and vice versa. If both Q and Q̅ are available, we say the circuit has "dual outputs". Most of the following types can be built as a "latch" that responds to the level of a signal, or as a "flip-flop" triggered by a change in the signal.