The religious symbol "IHS" is a monogram of the name of Jesus. This symbol is called a Christogram, and it comes from iota, eta and sigma, which are the first three Greek letters of Jesus's name.
In Latin, "I" and "J" are indistinguishable, and in Greek, "C" and "S" are sometimes interchangeable, so some versions of this Christogram read "IHC," "JHS" or "JHC." Some people think that these three letters are an abbreviation for "Iesus Hominum Salvator," a Latin phrase meaning "Jesus, Savior of Men." Others believe that it stands for "In His Service." Neither of these is correct. Other famous Christograms include the "????" used in the Eastern Orthodox Church and the "Chi-Rho," a symbol formed by superimposing chi and rho, the first two letters in the Greek word for "Christ."