Minecraft wiki entry for Memory, associated text: A RS latch has separate control lines to set (turn on) or reset (turn off) the latch. Many also have dual outputs. The oldest form of RS latch in Minecraft is the RS-NOR latch, which forms the heart of many other latch and flip-flop designs.
A T latch has only one input, the toggle. Whenever the toggle is triggered, the latch changes its state from OFF to ON or vice versa.
There are also SRT latches, combining the inputs and abilities of the RS and T latches.
A D latch has a data input and a clock input. When the clock is triggered, the data input is copied to the output, then held until the clock is triggered again.
A JK latch has three inputs: A clock input, and the jump and kill inputs. When the clock is triggered, the latch's output can be set, reset, toggled, or left as is, depending on the combination of J and K. While these are common in real-world electronics, in Minecraft they tend to be bulky and impractical — most players would use an SRT latch instead.