Dear Rabbi,

Who is Hashem? I have never found that name in the Bible.

Dear Marilyn Brewer,

We use the word Hashem to refer to G-d. Literally, Hashem means "The Name." The word Hashem actually appears in the Torah, as in "...fear the great and awesome Hashem (Name) - the L-rd your G-d." (Deutoronomy 28:58).

Essentially, the reason for using a substitute is out of respect. The actual name of Hashem has inherent sanctity and must be treated with respect; for example, it may not be erased.