Internet is defined as a network of computers which can be accessed by anyone having an internet connection. It is a collection of individual networks which are connected by physical optical fiber cables and intermediate networking devices called routers. An individual network is a network of computers. Router acts like a signaler at a railway station. It forwards  a message sent from a given computer to the right destination computer.

Computer A can send messages to computer D across the globe, even though they are separate networks. This is all possible because of an IP addressing scheme agreed upon by all devices on the internet. A computer participating in internet is identified by unique address called IP Address. It's an address made of four bytes separated by dots (IP address example:192.190.10.2). IP address (also called IPv4 address) uses 32 bits for addressing, however due to the rapid growth of the Internet, we’re running out of IP addresses. Hence IPv4 will eventually be replaced by IPV6 which uses 128 bits for addressing. IP address consists of 2 parts: Network ID and Host ID. Network ID identifies network and Host ID identifies a device in that network.

Communication between the computers on the internet occurs in the form of data packets containing destination IP address and source IP address. Source computer wishing to send a message to a destination computer will create a data packet comprising of message, source IP address and destination IP address. The data packet traverses across the internet to reach its destination, thanks to IP addressing, Computers Network & Routers. Intermediate routers will have all the information about the path of packet: Route information is stored in memory called route table in routers. When data packet arrives, router will determine the best route of a packet using destination IP address and route table. Intermediate routers keep routing the data packets till they reach destination computer.

It is difficult to remember this sort of IP addresses. To make things easier, we can map an IP address to a simple readable name called domain name. Example: Yahoo.com is the domain name for IP address 191.192.10.8. This mapping is stored in DNS servers. DNS servers map an IP address to domain name which is human readable. So, when we write google.com in our browser, the browser sends DNS query to the DNS server, which provides the IP address for that domain name-google.com. Now our computer can communicate with the google server, request information and load the website on our browser.