Star topologies connect each computer to a central hub so data can travel quickly between computers. This formation is the easiest to manage and upgrade but will fail if the central hub is down. Rings are more stable because data can only flow in one direction along a common path. However, travel is slower and prone to possible node bottlenecks. Lastly, bus topologies are laid out with each computer on a serial line with a terminator at each end.
Protocol is in fact the language communicated between devices.
As in society, two people talking in two different langauges will be very confused and the dialog will be near impossible. With the first, all computers may send and receive data, but when a collision occurs, one of the two computers will pause for a random amount of time and try processing again. Ethernet, Appletalk and Token-Ring architectures further define how the data is packaged and transferred. Cables are more than just wiring, they also provide protection for the data being carried within from electrical interference. Twisted Pair is by far the least expensive of the four.