After Link arrives in the Sealed Grounds, he enters the Sealed Temple, finding an Old Woman inside. Link is then told to head to the Faron Woods. After obtaining the Goddess's Harp from Zelda, Link returns to the Sealed Temple, where the Old Woman teaches him the "Ballad of the Goddess".
Eventually, Link is able to use the Master Sword to activate the Gate of Time within the Sealed Temple, allowing him to travel to the temple as it appeared in the past. Later, in order to learn part of the "Song of the Hero" from Lanayru, Link must plant the Life Tree Seedling in a patch of earth found in the Sealed Temple of the past. When Link returns in the present, the seedling will have grown into a tree bearing a Life Tree Fruit. This magical fruit has the power to cure Lanayru's illness, preventing him from dying.
Temple of Time
It is implied that the Sealed Temple became the Temple of Time seen in The Legend of Zelda: Ocarina of Time, given the Sealed Temple's very similar layout and the fact the Master Sword is placed in a pedestal behind a large pair of doors. The Hyrule Historia confirms this.
The Sealed Temple appears as part of the Sealed Grounds stage.