Who spoke to Moses on the Sinai mount

What is the meaning about the saying of the Most High: “And we called him from the right side of Toor, and made him draw near to Us, for mystic(converse).”
“But when he came to the (fire), a voice was heard from the right bank of the valley, from a tree in blessed ground: “O Moses! Verily I am Allah, the Lord of the Worlds.”