Yahoo! Mash was a website that was like a big playground where you could make a profile, just like you do on social media sites like Facebook and Twitter. It was a place where you could make friends with people you don't know, just like when you make friends at recess or in after-school programs.
You could also collect pictures, videos, and music on your page and share them with your friends. It was like everyone had their own special toy box that they could share with others.
Yahoo! Mash was created by the company Yahoo! as a fun place to hang out online, but it didn't last very long. Just like how some playground games only last for a little while, Yahoo! Mash closed down after a couple of years. But don't worry, there are still plenty of other websites where you can make friends and share your favorite things with others!