What's on the internet? Well, that's a bit of a tricky question.
The internet is a large network that links millions of computers from all points of the globe with the express purpose of allowing people to share information with each other. The invention of the internet can be traced back to 1958 (it's not at all that old), when the Advanced Research Projects Agency was tasked with developing an new form of technology for the US military. This was in light of the USSR launching their Sputnik Satellite, so the US was desperate to out do them. Computers, which were once as large as vehicles, slowly became smaller and more accessible to the public. In 1969, the first connection between two computers was successful and it began a new age in communication.
Now, to clear the air a bit, the Internet and the World Wide Web are not the same thing. They are often confused, and honestly, most people mean the World Wide Web when they say things like "I found it on the Internet". The Internet is simply the network that connects computers (and now other devices) together. In 1969, the only thing that computers were capable of was sending emails, though it wasn't until 1976 that an email service provider was invented. The World Wide Web did not show up until the year of 1993.
Certainly, what the question "What's on the internet?" is asking has to do with the information being shared on the WWW, via the Internet. That question is answered very simply, as today almost anyone who as access to a computer connected to the internet has the ability to access the World Wide Web. Anyone can create a webpage that will share any sort of information. Millions of books and studies, guides and services, as well as a plethora of opinions are available to anyone with just the click of a button and a few keywords into any search engine.
The internet, and by extension the WWW, is available to us with the express purpose of sharing information. So if you want to learn about the Milky Way Galaxy, you can find a mass of information from NASA's official website. If you want to know how many licks it takes to finish a hard candy, you can find dozens of studies that have been conducted by more than one curious college student. If you want to find your favorite movie and purchase it without the hassle of going through the bins in your local stores, you can easily order it from a service provider. To say that you can get anything thanks to the internet is not even a slight stretch.
Thanks to the connection of literally millions of people from every country on this Earth, you have access to an amazing amount of information. The internet makes things a lot more simple and though you have to pay a sum for its use, it's no doubt at all that it is very worth it.