What is the Internet?

The Internet is a worldwide network of computers all connected. When you are connected to the Internet, your access to the World Wide Web, which is a library of information pages.

For further reading, explore Things I Learned 20 Google Book.
How do you connect to the Internet? What is the function of an ISP?

Before you begin to explore, you ISP plan. An ISP or Internet service provider is the company that lets you access the Internet and other Web services. These provide various ways to connect, including dial-up, cable, faibar optics or Wi-Fi. These determine the speed of your Internet access to various connections.
How is my mobile phone Internet reaches? It is different from the desktop?

General cell phone connects to the Internet from the wireless signal, which is used for phone calls. Your phone connects to a cell tower area, which you connect to the Internet. Since transferring data between mobile devices and the Internet can be expensive, so service providers spend for data plans.