A nettop is a computer that is really small and doesn't take up much space. It is like a tiny version of a regular desktop computer that you might see at school or in your parents' office.
Think of it this way: You know how small toy cars are compared to real cars? Nettops are like the toy cars of computers because they are tiny and not as powerful as the big ones. They can do simple things like browsing the internet, word processing, and emailing, but they can't do the really complicated things that the big computers can do.
When you want to use a nettop, you might plug it into a monitor, like your TV, or a small screen on the nettop itself. Then you can use a keyboard and a mouse to control it, just like you would with a regular computer.
Nettops are great for people who don't need a really powerful computer, like kids who don't do too much work on the computer, or older people who mainly use it to read the news and check email. They are also good for people who don't have much space in their home or office for a big computer.
So, a nettop is a really small and basic type of computer that is good for simple tasks and doesn't take up too much space.