Okay kiddo, do you know what a piano is? It's a big instrument with lots of keys that you can press to make different sounds.
Now, sometimes people like to play music together with other people. When three people play together, it's called a trio.
But what kind of music do they play? Well, there are lots of different pieces of music that are written just for a piano trio to play. These pieces are called piano trio repertoire.
Some of these pieces are really famous and have been played by pianists, violinists, and cellists for a really long time. They're like old friends that everyone knows and loves.
Others are more modern and maybe not as well-known yet, but they're still really fun to play and listen to.
So when a piano trio gets together, they can choose from lots of different pieces to play. It's like having a whole toy box full of different games to play with!