In simple terms, It means Computers connected.

What is the Internet?

It is the collection of computer networks, for example, our phones are connected to our PC which is itself connected with wifi or routers and that is connected to other peoples' devices and these connections are spread across houses, cities, countries and so on so, this entire connection on a global scale is known as the Internet.

How did the Internet and Networking start?

The Internet we know and use today was a result of an experiment, ARPANET, the precursor network to the internet.

• Sputnik launch
  It was in the midst of the Cold War, on October 4, 1957, that the Soviets launched the first man-made satellite into space called Sputnik It was the world's first-ever Satellite. Americans feared because of that floating object, the Soviets were not only ahead in science and technology but were a threat too. They can now spy on their enemies, and win the cold war and nuclear attacks were also possible on American soil.
  So Americans started working more on science and technology. After the Sputnik wake-up call, the space race started. After that in 1958, the US Administration funded various agencies, one of them being ARPA.

• ARPA
  ARPA stands for Advanced Research Project Agency. It was a Defence Department research project in Computer Science, a way for scientists and researchers to share information, findings, knowledge, and communicate. It also allowed and helped the field of Computer Science to develop and evolve. Read more

• ARPANET
  At the beginning of ARPA, they set up their workspace in four different places MIT, Standford, UC LA, and UTAH. Because ARPA had facilities to share then to communicate with each others' workplaces they built something called ARPANET and from there the concept of Computer Networking came to know.

Protocols

Different types of things we try to send over the Internet like text, images, emails, videos, secured files etc.
For different files, different kinds of rules will be required. so, the rules set up by people that, how a particular data is going to be shared over the Internet are called Protocols.

World Wide Web

www(World Wide Web), this is something we all are aware of but how did it start? so in the early age of the Internet, it was used by Computer Scientists who used to share their research papers with other Scientists. In between these papers, they wanted to attach links that were connected to other files but earlier websites used to be static( Single page).
Sir Timothy John Berners-Lee an English computer scientist best known as the inventor of the World Wide Web invented www which stored all the websites and helps them to act dynamically (multi-paged websites).

Why do we need Protocols?

Imagine you have made an application and you have established your particular rules to access your application and there is another person who also built an application with his own set of rules. so now will you and that person will be able to communicate with each others' applications? The answer is no. You can't because none of you know about each other's methods that is why The Internet Society has made a set of rules for networking which are called protocols and everyone has to follow those rules.

Client-Server Architecture

The client's computer sends a request to the server and the server responds to that request and returns a webpage that is visible to us on our computers. let's say you search Google, your Computer will request it to the Google Server, then whatever resources or files are there within Google it will be returned to your Computer.

Types of Protocols

• TCP(Transmission Control Protocols)
  It ensures that data will reach its destination and will not be corrupted on the way.

• UDP(User Datagram Protocols)
  when we do not care about whether all the data is being transferred or not. for example - In video calling sometimes because of bad network quality video call lags or images are not clear there the concept of UDP is used.

• HTTP(HyperText Transfer Protocols)
  The format of how client requests to servers and servers responded to clients comes under HTTP.

How the Data is transferred?

Every data in the computer is in binary form, 0s, and 1s so, it doesn't make any sense to send the entire data in a single go. Suppose you have to send a large file will it be possible to send the entire file in a single go? No, it comes in chunks. Similarly here also whatever we are doing like watching movies or serving over websites data we will get in packets.

What is an IP Address?

When we request anything over the internet suppose we write Google, then how does it know to which server it has to request to get the data? So, every single device on the Internet that can communicate with each other they are identified by something called IP Address.

format - ** X . X . X . X**, every single X can have numbers from 0 to 255.

command to check your Computer's IP Address

How does IP Address work?

• ISP(Internet Service Provider)
  this is your telecom company from where you get the Internet

• Modem/ Router
  Device to connect with the Internet. It has an IP Address that is a Global IP Address. whichever device is connected to this modem will have the same IP Address similar to this device.

• D1, D2, D3, D4
  These devices are connected to the same modem/Router so all of them will have the same IP Address. The modem from which these devices are connected that is going to decide, which responded data by the server has to be sent to which of these devices.