On A 3-way, there’s an extra terminal, known as the “widespread.” Power comes in on the switch over the prevalent, then two “traveler” wires hook up the primary switch to the second on the brass terminals. These are definitely only schematic diagrams to explain about the different styles of arrangements https://wiring-systems01695.dgbloggers.com/35241940/the-2-minute-rule-for-wiring-to-lights