Okay, sweetie, so Facebook is a big computer program that lots of people use to talk to each other and share pictures and stuff. But sometimes, bad people make little bits of computer code called "malware" that can sneak onto your computer when you use Facebook.
This malware can do bad things, like steal your personal information or mess up your computer. It might look like a game or a cool picture, but it's really something bad that can hurt your computer.
To stay safe, you should always be careful what you click on in Facebook. Don't download anything from people you don't know, and make sure you have a good antivirus program running on your computer to catch any malware that might sneak in.
If you ever see something suspicious on Facebook, tell an adult or a trusted friend right away. They can help you stay safe and make sure your computer isn't hurt by any bad stuff.