The Jesus Prayer is an ancient way of prayer that today is used by millions of Christians. While associated with Orthodox and Eastern Catholics, it’s also promoted in the Catechism of the Catholic Church.
I came to know the Jesus Prayer after studying the Desert Fathers. St. John Cassian (360-435) wrote about the monks of Egypt, the Desert Fathers, who promoted a form of prayer that repeated a few words or a short phrase as a way of practicing ceasless prayer. In time this kind of prayer spread among monks and developed into the formula now known as the Jesus Prayer.
You can find out more about this ancient prayer practice from these websites: