If you only plan on networking 2 PC's together, you can do it without a hub at all. This is a specially wired cable that is ONLY used to connect 2 PCs. In a network with 3 or more PC's, the hub does the crossover work. A crossover will NOT work with most hubs, although a few will. Networking cable has 8 insulated wires in it, surrounded by an outer insulated casing.
Cable comes in shielded and non-shielded varieties.
The shielded cable is a little bit more expensive, but well worth it, because electromagnetic interference can wreak havoc on your network cables. The protocol is the language your network uses to communicate. I only use the 2 for simplicity sake. Too many protocols degrade network performance and slow your system down. Put it in a central location in relation to the 2 PC's that are farthest away from each other.