I have some trouble to make a difference between IP address, FQDN, domain name... Tell me I'm wrong but an IP address represent a computer (a machine). And a domain name is an other representation of a an address ip, and to make the link between IP address and domain name, DNS is used. But I saw some domain name which have many ip address, and some IP address which have many domain name linked. How is it possible ?
I'm really confused :s
Thx
An IP address, either version 4 or 6, is both an identifier and a locator (it shows how to reach a specific element connected to the Internet).
More specifically it is tied to an interface, and a computer can have more than one interfaces. In fact, yours always have at least 2 addresses because it has 2 interfaces by default: localhost (127.0.0.1) which maps to itself (so it is the same name everywhere) and some IP address given by your ISP because you have an Ethernet or a WiFi interface.
A name, hostname, domain name, Fully Qualified Domain Name are all identifiers for human consumption, computers mostly do not use them.
The DNS system and the nameservers participating in it, among other things, allows to map a given name to a set of IP addresses.
A server name can map to multiple IP addresses for both fail over and load balancing: heavily used resources are split between many different servers with all their own IP address (there are ways also to make multiple servers all appear under the same IP everywhere, this is called IP anycasting).
As for "some ip adress which have many domain name linked." you will need to explain yourself a little more. Where do you see that? In the DNS, the PTR records allows you to map one IP address to one name, this is seldom used but it exists, and you have multiple IP addresses in multiple PTR records that all maps to one given name, but this is very little impact in real life.
