A domain name is a unique name that identifies a website or computer on the Internet.
Although you can identify a computer by its IP address — for example, 192.168.1.50 — numbers are not very easy for people to read or remember. This is why domain names are useful — they serve as “nicknames” for websites and computers. A domain name points to an IP address, and you can then use the domain name, rather than the IP address, to access the website or computer.

How to set up domain?

just go into domain panel and set NS record or A record to your webhosting,
Ns record example ns1.webhosting.com, A record is IP of your webhosting. you chose one of them .
usualy get 5 minutes – 48 hour to resolve.

Some  free domain :
co.nr
cz.cc
co.tv
co.cc