A public computer is like a toy at a playdate that all the kids can share. It's a computer that belongs to a group or organization, like a library or a school, that anyone can use.
When you use a public computer, you have to share it with other people, just like you share toys. This means you might not be able to save your work and come back to it later because someone else might use the computer and erase everything you did.
Also, because lots of different people use public computers, they can get dirty and sometimes have viruses or other bad things on them. So it's important to be careful when using a public computer and make sure you don't download anything or visit websites that could harm the computer or your personal information.
Finally, remember that a public computer is not your own computer, so you should always log out of any accounts you use and not save any sensitive information on the computer.