Three Way Wiring Diagram With Two Lights. The black hot wire connects to the far right switchs common terminal. Three wires between the two end switches probably using 3 core and earth cable.
Two wires between each switch. Here the source is at the first switch sw1 and 3 wire cable runs from there to the first light l1. In this diagram the source for the circuit is at the light fixture and the two switches come after.
A 2 way switch wiring diagram with power feed from the switch light.
This can be confusing. Most likely to be found with wires in conduit. Usually the third wire passes the middle intermediate switch but is joined in a separate terminal block. If both the switches are up or both are down the circuit is complete and the light turns on.