Okay, kiddo, so a long time ago, people didn't have all the fancy technology we have today to connect and talk to each other. They didn't have phones or computers, and they definitely didn't have the internet. But they still wanted to be able to communicate with each other, especially scientists and researchers who were working on important projects.
So, a group of people got together and came up with an idea called "Arpanet." This was a special kind of computer network that would allow people all over the world to share information and communicate with each other. Arpanet was created by the United States Department of Defense in the 1960s and was the earliest version of the internet.
Imagine you have a toy phone that can only call your best friend next door. But your mom and dad also have toy phones that can call their friends. This is like what Arpanet was at first, but for computers. Scientists and researchers could use their computer "phones" to communicate with each other but only on certain "lines" that were set up.
Over time, Arpanet grew and evolved, kind of like you growing and learning new things. More and more computers were added to the network, and eventually, people could talk to anyone on Arpanet from anywhere in the world. It was very exciting because now, people could share information and work on important projects together, even if they were in different countries.
So that's what Arpanet was, kiddo - a special computer network that allowed people to communicate and share information. It was the beginning of the internet, which we use for lots of things today, like playing games, watching videos, and talking to people far away.