Are God and Lord two names for the same entity?

Neither God nor Lord are names. Both are titles. The name of God in the Hebrew bible is YHVH (the pronunciation is unknown).

The Almighty makes it abundantly clear to us to NEVER use the name of another deity.

Exod. 23:13 (Almighty speaking) "Now concerning everything which I have said to you, be on your guard; and do not mention the name of other gods, nor let [them] be heard from your mouth."

Answer:

God is the English word translated in our bibles from the Hebrew Elohim and the Greek Theos. Lord is the word translated from the Hebrew Adonai or the Greek Kurios. Lord comes from the Old English hlaford which means master of the house or ruler. It is an acceptable form of Adonai, a title that many of the bible characters (i.e. Moses, Abraham) have called God. In fact, God refers to himself as Adonai on many occasions.

Finally, "Yahveh" is just one of many possible pronunciations of YHWH, the English rendering of the Hebrew letters yod hay vav hay, God's name. No one knows with 100% certainty how to pronounce the name; therefore, it should never become a point of contention.

Answer:

The spelling and pronunciation "Yahweh" is Christian in origin and is not used by Jews. The word "Adonai" literally means "lord;" and we use it to refer to God (and for no other purpose).