Appletalk is also used but usually runs on ethernet for the bottom three layers. Some other network protocols you may hear about. These are actually operating systems that include network functions. We will not address them specifically today because they can all use the same first three layers of the OSI model and the specifics are beyond the scope of today's talk. What this mouthful boils down to is enforced electronic politeness.
All devices listen to the network constantly.
When a device wants to transmit on the network, it ensures that no other device is talking at the moment and then transmits. If two devices happen to transmit at exactly the same time then they hear each other and both stop transmitting. Both devices wait a random amount of time and then the process starts again. Although this works well it has a few problems. This keeps any other device from transmitting.