All lights on an aircraft are communication.
Nav Lights: Display that the aircraft is powered and the radio is set to the ground controller frequency (so it can be hailed by them)
Beacon: Engines about to come on (/are running)
Taxi light: Display that the aircraft will move independently over the platform.
Strobes: Aircraft is now part of the airborn traffic (the moment it enters a runway, so also when only crossing)
Landing lights: hampered flight below 250 knots below FL010
To my knowledge the runway turnoff lights however are optional, as they just give the flight crew extra visibility in bad weather or dark circumstances.