What is the soundex?

Question:

What is the soundex?

Someone suggested I search soundex for my husbands realitives. Last name Golliday, have seen it spelled several ways.
I don't know what the soundex is and/ or how to use it

Best Answer - Chosen by Asker: soundex is how the name could have sounded to a translator either in census records or immigration records-
So if the name is Golliday- try saying it with an accent- it could come up as Holiday, Golidae, or Galiday
Use the soundex feature on websites like Ancestry.com and they will come up with possible matches for you