"YHVH" is a name that is usually translated as "LORD." It is used approximately 7000 times in the Bible (Tanach), more than any other name for God. It is also referred to as the "Tetragrammaton" which means "The Four Letters" because it comes from four Hebrew letters: Yud, Hay, Vav, Hay. It is generally believed that these four letters represent the tenses of the Hebrew word for to be. That is, HVH (Hovah)=to be, HYH (Hayah)=was, and YHYH (Yi-yeh)=will be.
God revealed Himself as YHVH in Exodus 3 in conjunction with the creation of Israel.