So, imagine a musical instrument that looks like a rectangle with lots of strings on it. That's a baltic psaltery! It's sometimes called a zither.
To play it, you pluck the strings with your fingers or a pick. It makes a pretty sound that's like a combination of a guitar and a harp.
People in the Baltic region of Europe have been playing psaltery-type instruments for a long time, even before we had computers and TV and all the cool stuff we have now. They would play them for fun, for ceremonies, or just to make music with their friends and families.
So, if you want to try playing a baltic psaltery, just remember to pluck the strings gently, and have fun making music!