It is Hebrew.
In Hebrew it is written like this שלום
Writing it in another language is called transliteration. Many words we use today are actually from another language and were originally written in another alphabet. Shalom is one of those words.
Vodka, Czar, Gulag, Kremlin, Mammoth, Intelligensia are used in English but were originally written in the Russian alphabet.
Dojo, Judo, Shogun, Zen, Futon were all written in the Japanese alphabet first.
Tush, Bagel, Klutz, Goy, Kosher, Lox, Putz, Glitch were all written in Yiddish first.
Jar, Lime, Magazine, Soda, Candy, Coffee, Cotton, Sofa...are all words we think are English and actually they were first written in Arabic and come to us from Arabic countries. We simply transliterated them.