A virus hoax is when someone makes up or spreads a story about a computer virus. It's like a regular hoax, where people lie or make something up to try to scare people or trick them into doing something.
In this case, they lie or make up something about a computer virus and shares it online or with friends. They could tell people that a certain program or website has a virus or that the virus will do something scary or bad. The truth is that usually these stories are not true, and there's no virus involved.
It's important that you don't believe everything you see or hear online, and be careful about what you share with others.