Who is the Lord God in Exodus 20:2?

The Lord God in Exodus 20:2 is Jehovah God. The context contrasts this with Elohim, the almighty God of all, and identifies Jehovah as the One intrinsically involved with the nation of Israel. Thus the Lord God is Jehovah, specifically connected to Israel.

Les explains that Exodus chapter 20 verse 1 uses God, which is Elohim, the almighty God over everything, not just Israel. Then verse 2 moves to the Lord God, which is Jehovah God, who was intrinsically involved with the nation of Israel. Les also notes that the law was specifically given to those under the law, yet Paul says all the world might be brought under its guilt. So the law was given to Israel but still has control over the whole human race.

Exodus 20:2

I am the LORD thy God, which have brought thee out of the land of Egypt, out of the house of bondage.

Why does Exodus 20:2 say 'the Lord God' instead of just God?

Exodus 20:2 uses 'the Lord God' because it identifies Jehovah, the God intrinsically involved with Israel, whereas verse 1's 'God' is Elohim, the almighty God over all. This signals the law was given specifically to Israel though it exposes all the world's guilt.