The Genevan Psalter is a really old book that has a bunch of songs in it that people used to sing in church. The book was made a long, long time ago in a city called Geneva, which is in Switzerland. People who made the book wanted to have songs that everyone could sing together, no matter what language they spoke. So, they made the lyrics in Latin which was the language that most people could understand at the time.
The songs in the Genevan Psalter are special because they have a very simple tune that is easy for everyone to sing. They are also special because they were made to be sung without any musical instruments. People would just get together and sing the songs without any help from other machines or things.
The reason why the Genevan Psalter is still important today is that it is part of the Christian tradition. Christians around the world still sing the songs from the book, and new versions of the songs have been made in many different languages. It is like a very old piece of history that still lives on today.