Passive Multiples essentially copy the signal, you plug into the passive mult and it takes copies to the output jacks. These are the cheapest way to duplicate a signal. There are 1U or 3U modules but also come in different forms such as the TipTop Stack Cable and Intellijel Hub that offer external multiples that don't take up extra space.
The Buffered Multiples take a copy of the voltage from the input signal to the output signal. They draw power due to the circuitry and keep tuning in tact and rhythmic precision with multiple outputs from a dedicated input. They can come in 1U or 3U forms such as the Intellijel Buffered Multiple.
Logic Multiples are specialized binary versions of buffered mults. With these, you send a signal into a circuit that measures its level. If the input is below a certain reference, sends out 0 volts. If it’s above a certain reference, it sends out a +5 volts or full voltage.
While passive mults are affected by both input and output, with buffered (active) mults, what is happening on the output does not affect the input and logic mults are scarcely used but can provide useful in certain scenarios.
Happy Patching :)