This is a nice guide for surviving the Internet. The name of your computer has to be unique - picking any celebrity or cartoon character is likely to be duplicated by someone else. Something generic like your room number works best, but if you don't feel comfortable with that try to be as original as possible. The name mentioned above refers to Microsoft Networking. The real DNS name of the IP you receive from the DHCP server is fixed.
Ethernet is the name of a technology computers use to talk to each other.
The addresses make it possible for other computers to know who's talking and to whom, in much the same way you get John's attention in a crowd by starting your comment to him with his name. This address is assigned when the network card is manufactured and cannot be changed. This address is different from the IP address earlier. Your MAC address is more like your room number, whereas the IP address resembles more the mailing address of your residence hall. The MAC address consists of six bytes , which are usually expressed in hexadecimal notation, resulting in addresses that are 12 characters long.