In the seventh aliyah G-d tells Moshe to write down all these words into the written Torah. Rashi points out that Moshe is not permitted to write down the oral Torah, which explains the written Torah.
Moshe was up on mount Sinai for 40 days and 40 nights without eating or drinking. When Moshe came down, beams of light were visible projecting off Moshe's skin, and Aharon and the people were afraid of him. (Rashi says these beams of light were from G-d touching Moshe's face.)
Moshe taught the people the words of Torah that Moshe heard on the mountain. Moshe wore a veil on his face when he talked to the people from that time on, but took it off when speaking to G-d.