IHS stands for the name of JESUS, with various explanations having been given over the years for the amalgam. It was used by early preachers on icons, banners and insignias who promoted devotion to the feast and to the name of Jesus, Himself. Today you will see he insignia in church art of all kinds. In some churches, one could spend a great deal of time counting the number of times the insignia appears on pews, windows, altars and more. While counting, reverently holding the name of Jesus in prayer would be a good pious practice.