The Internet is all about data transfer. that's all. Now you know what is internet. What? Not enough? Okay, let's understand it in another and more detailed way.
Suppose you have some movies in your pen drive and you want to watch them on your computer. What will you do? You will simply insert your pen drive into your computer, copy-paste movies and start watching them. You transferred some data/files from your pen drive into your computer that is physically connected.
Now suppose you have two laptops and you need to transfer movies from one to another and you don't have a pen drive. How will you transfer? You would need to somehow physically connect both laptops with wire (LAN) and transfer movies. What if one laptop is in another city, another country or another continent, how will you connect both laptops? Would you use thousands of miles of long LAN cable to connect?
This problem was very huge and we needed to somehow connect every computer in this world to each other so that data transfer could become easy. Then some big investors gathered and made a company that laid thousands of miles of long cables across the ocean and connected every continent, and every country to each other via those cables. These companies are called Tier-1 ISPs (Internet Service Providers).
All countries are connected. Now, it's time to connect states or provinces within a country. Companies that connect interstates via internet cables are called Tier-2 ISPs (Internet Service Providers). and companies that connect intercities via internet cables are called Tier-3 ISPs (Internet Service Providers).
Tier-3 companies provide internet services to the end-user in the form of broadband/wifi so that you can access every computer in every city of your state because Tier-3 ISP only connects cities in one state. Tier-3 ISPs make deal with Tier-2 ISPs and rent national internet cables so that you can have access to your whole country's internet. And at last, Tier-2 companies rent international internet cables from Tier-1 ISPs so that you can connect to the whole world. Tier-1 ISPs charge from Tier-2 ISPs, Tier-2 ISPs charge from Tier-3 ISPs and Tier-3 ISP's charge from the end-user to use their internet services. Those internet cables also connect to all SIM towers so that you can access the internet from your carrier sim card.
Now you know that the whole world is connected through wire cables. That's where the term "web" (a spider web that connects every point) came from. A web that is connected worldwide ( www - world wide web).