Zelda 1 before the deku tree - xackery/xackery GitHub Wiki
The Great Deku Tree is the fatherly guardian of the forest who safeguards not only the dense land around him, but the small population of beings that live in his shadow. In Ocarina of Time, the famed Kokiri praise and worship the massive tree, sharing a home in the Kokiri Forest, while in The Wind Waker, these beings are none other than the Koroks, timid wood creatures who live collaboratively with the talking tree in the arboretum that is the Forest Haven. http://zeldawiki.org/Great_Deku_Tree
The Deku Tree made his first appearance in Ocarina of Time as the guardian of the Kokiri and of their forest. He protects the Kokiri's Emerald, one of the three Spiritual Stones.
At the end of the day, though, http://xackery.com/gaming/zelda-ocarina-time-part-1-deku-tree/ is where to go.