# angel of Yahweh

This was Yahweh himself appearing as an angel, and not just an angel that Yahweh sent. "Yahweh appeared as an angel" .

# Yahweh

This is the name of God that he revealed to his people in the Old Testament. See the translationWord page about Yahweh concerning how to translate this.

# behold

The word "behold" here shows that Moses saw something that was very different from what he expected.