What is Internet
Internet is a worldwide accessible public medium of interconnected computer networks. The networks operate with the help of the network protocols, most important of which are IP (Internet Protocol), TCP (Transfer Control Protocol) and UDP (User Datagram Protocol). These protocols define the way of communication between devices connected to the network. Each one of these devices could be a server of service (or data) or a client of services (or data). On that basis we can separate the devices into Servers and Clients. Very often in the real world one device (computer) is at the same time a server and a client. We can add that there also exist and a big amount of support devices which ensures the proper and flawless work of the network.
Services and Servers
The service is a specific activity for the server, which it provides to the clients for use. Typical services for the Internet are the electronic mail, the file transfer and, of course, the access to web documents. The word “server” may have different meanings. For example, the server may be called the hardware (the computer), which usually is designed for non stop work. Therefore these machines are highly reliable and efficient in operation. Another meaning of the word “server” is for the program which follows clients’ requests and responds to them in an appropriate way. Often the server is a combination of both, that is the machine (the computer) designed to perform a specific service. In short, they are called with the name of the service, for example; a web server, a mail server, etc. In order to have a web site we need exactly a web server. The web server can give clients access to files of different types. For example; text files (HTML documents), pictures, PDF documents, multimedia files and many more. The protocol for exchange of information between the Web server and the client is HTTP (Hyper Text Transfer Protocol). In order to provide access to our Web server for all clients, we need another server called a DNS Server.
The Domain name is a name, which is assigned to a particular server. The Domain name is needed because the base protocol for the Internet is IP and according to the protocol every server has a numeric encoded address (IP address). And here the DNS server helps us because it converts the domain name to IP address and allows us to access the servers only by names. Of course these domain names should be reserved and therefore they are paid. So, if we want to have a world wide accessible web site we must have a domain name, a DNS server and a Web server.