So, you know how sometimes in church or at a concert, people sing songs? Well, those songs usually have something called chords.
A chord is like when you play different notes on a instrument, like a guitar or piano, at the same time and it makes a really pretty sound.
The book in the Bible called Psalms has a lot of these songs in it, and some people like to play them on instruments to make them even more special.
So, a "Psalms chord" is just a special combination of notes played together to make the music for a song in the book of Psalms. It's like a secret code that musicians use to make the music sound just right for the words in the song.