1. Straight through cable: This is also known as patch cable. A straight through cable is used to connect a computer to a hub or a switch.
2. Crossover cable: A crossover cable is used to connect one computer to the other computer B without using a switch or hub.
3. Rollover cable: A rollover (also known as console cable) is used to connect to routers for configuration purpose.
Also, you can't connect the Ethernet port on PC to another Ethernet port on a router using a straight through cable. You need crossover cable for this purpose. Also, the PC need to have a network card, and appropriate networking protocol stack properly installed and configured.