DNS can be a rather complicated matter.
Too cut things short, here is a discription of what it does, and why it does it.
DNS, as you may well know, stands for "Domain Name Server". It is responsible, for mapping domain names to IP addresses.
The Internet uses TCP/IP to comunicate. With this, each device connected to the Internet, must have at least 1 IP address.
IP address are 32bit binary number, that are presented in 4 dotted decimal numbers (EG 192.168.0.2).
The problem, was that you could not allways remember what machine a IP refered to, and thus, some naming convention was required.
This is what DNS does. It is responsible, for converting an hostname or domain name into a IP address.
When you request information on the internet. The software, must first make a request to a DFNS server, an ask for information about the hostname typed in.
Because TCP/IP was built on IP addresses, all connections, must be to IP addresses.
Registrars ask for 2 servers, for redundancy. Should 1 server fail, a backup server will kick in.
DNS Pools are banks of machines, responsible for managing many domain names. EG, 10 machines answering DNS request for 100's of domain names. This is done for load ballancing.
Domain name server come with most versions of *nix, failing that, they are downloadable for free (Bind is the most widly used DNS server).
If you require the use of DNS server, you should look towards your ISP. They should help you getting started, allthough they will want money for this.
The company you registared the domain with, will most likely provide DNS services too.
As for the ability to point one.place.org to one area of the world, and two.place.oeg to another. It's all just the way it's mapped.
Think of DNS servers as telephone directories. Where you telephone directory is just for your area, the DNS directory is for one domain (allthough it can manage hundreds, this is just an example). You look through the telephone directory, to get you result, in much the same way a DNS server does. Instead of getting a telephone number, it gets an IP address.
This IP can be anywhere in the world. DNS servers just reply with this IP (this is there primary use). DNS server have no need to distinguish the geographical location of the machine on the IP.
DNS servers are not for hosting. They are just used to map hostnameA, to IPA, and so on.
DNS servers are allso used to work out, how to get e-mail, from one server, to the computer, that you collect your e-mail from.
EG, my e-mail address is
ppslim@postmaster.co.uk. When you send a e-mail, it is sent to your ISP's server. In turn, that server, will ask a DNS server, for information about the domain postmaster.co.uk. In this information, is listed what hostname, is responsible for collecting e-mail for the postmaster.co.uk domain. Your ISP's server, then connect to this machine, and send the mail on.
DNS and mail mapping are much more somplicated than that, and this is just a brief outline, on how it works.