Moses sees a bush that is burning but not consumed. He hears a voice telling him to take off his shoes because it is a holy place. This is not because it is inherently holy, but because God is in this place. God tells Moses that He has seen His people's suffering and that He will uses Moses to deliver them from Egypt.
Moses protests, asking why God has chosen him. God explains that He will give Moses the words to say. God also gives Moses the name YHWH, meaning "I am who I am," to give to the Hebrews as the name of the God of their ancestors. This name was already given in Genesis, but it may have fallen into disuse while in Egypt. This name tells us something about who God is. He is eternal, is self-existent, and the source and sustainer of all that exists.
God turns Moses' rod into a snake and back into a rod, and shows him other signs that show that He is the Lord of over life and death, and over sickness and healing. He is the Lord of Abraham, Isaac and Jacob, which indicates that He continues to be their god, implying that there is life after death.
Moses protests that he is not eloquent, but God will use Aaron to speak for Moses. God will harden Pharaoh's heart, though there are many times when Pharaoh will harden his own heart, and Moses tells Pharaoh that if he does not let the Hebrews go, He will take Pharaoh's firstborn.
Upon returning, God tries to kill Moses for not circumcising his sons, but Moses' wife Zipporah circumcises their children and saves his life.