Re: can anyone explain the clean working of this?

Karinna has it right, if not a little hard to understand if you dont know about it in the first instance.

easiest way to explain it -

you need several things to connect to the internet these are:
1)a physical connection (a cable, or a wireless signal, something to transmit the data across)
2)internet protocol (IP) this is the IP part of TCP/IP and UDP/IP, this is the part that gives your computer an address on the internet.
3) a control protocol (TCP or UDP) there are only two. you have to chose one.
TCP makes it reliable (this means that if I send 1 packet to you then you send me a reply saying that you got that packet and that its ok for me to send the next packet to you [syn/ack challenge handshake]) UDP is smaller (and therefor faster) but doesnt provide for reliability, you can loose packets)

4) an application - an html browser, telnet, a webserver, ping (which uses icmp), bittorrent,RTSP [realplayer]

do some research on the OSI/ISO 7 layer model to find out the exact details =)