Okay, so you know how you have a computer at home or school that you use to do your work and play your games? Well, a PC-on-a-stick is like a tiny version of that computer that you can carry with you anywhere you go.
Imagine you have a stick, like a big USB drive. Instead of just storing files on it, this stick has an entire computer inside it! So, you can plug it into any screen - like a TV or monitor - and it will turn that screen into a computer.
This special stick has a tiny processor, some memory to help it think, and even some storage space to save your files and pictures. You can use it just like a normal computer, but it's smaller and more portable. It can even connect to the internet so you can watch videos or play games online.
It's like having a mini computer that you can take with you and use on different displays wherever you go. It's pretty cool!