Windows Vista is an old computer program that was released by Microsoft many years ago. Just like how you have games on your tablet or phone, people used to use Windows Vista to do things on their computers.
Windows Vista had a lot of new features to make things easier for people to use, like a new start menu and ways to organize your files and pictures. It also had some cool features like transparent windows and a new search tool.
But some people didn't like Windows Vista because it was slow and could be hard to use. Eventually, Microsoft stopped updating and supporting it because they made newer and better programs.
So, Windows Vista was a computer program from a long time ago that people used to use on their computers, but now it's not really used anymore because there are newer and better programs out there.