What exactly were the cloaks of skin that Hashem made Adam and Chavah?
Rashbam: Cloaks made of skin that covered their entire bodies.
Targum Yonasan: Clothes of glory which Hashem fashioned from the shed skin of the snake. 3
Riva, Rosh: It was from the flayed skin of the Livyasan.
Chizkuni, Riva: I.e. they had no hair, unlike Rashi's other Perush.
The Seforno points out that Hashem fashioned the cloaks, without Adam and Chavah having to do anything. This is reminiscent of the time of Mashi'ach, when Eretz Yisrael will produce loaves of bread that are ready to eat and fine woolen clothes that are ready to wear (as the Gemara states in Shabbos 30b).
See also Ba'al ha'Turim.
Why did Hashem need to make clothes for them? They already made for themselves from fig leaves!
Riva: The fig leaves covered only their Ervah. Refer to 3:10:1:1*.