They are the standard footwear for the Kokiri race and fit Link both as an adult and a child and are very light. Link begins his adventure with these boots already in his inventory.
Unlike the Iron Boots and Hover Boots, the Kokiri Boots do not allow Link to weigh himself down or hover in the air, respectively. However, unlike the Iron Boots, the Kokiri Boots do not slow Link down, and unlike the Hover Boots, the Kokiri Boots do not cause Link to slip.
The Kokiri Boots return in the Nintendo 3DS remake of Ocarina of Time, though they do not appear as an actual item due the Iron Boots and Hover Boots being changed to regular items to make switching easier (similar to how the Iron Boots are used in The Wind Waker and Twilight Princess). However the Kokiri Boots still appear as Link's standard footwear and allow him to move without slowing him down or cause him to slip. Link will switch back to his Kokiri Boots automatically when the Iron Boots or Hover Boots are unequipped.
Though they do not appear as actual items in the game itself as Link cannot change tunics or boots in Majora's Mask (due to the fact that their role is replaced by the various masks), Link wears his Kokiri Boots and Kokiri Tunic during his adventure in Termina and are among the few pieces of equipment from Ocarina of Time that Link retains at the beginning of Majora's Mask. Interestingly, the boots apparently change along with Link when he uses transformation masks.
In Breath of the Wild, the Trousers of Time leg armor refers to the Kokiri Boots and Tunic. The Trousers of Time can be obtain by using the amiibo Rune and the Link amiibo of the The Legend of Zelda: 30th Anniversary series.
As the manga is based on Ocarina of Time, Link wears the Kokiri Boots and Kokiri Tunic during the manga's retelling of the events of Ocarina of Time.
Interestingly during his Triforce Slash-like combo, Young Link with remove his Kokiri Boots and don the Pegasus Boots to increase his dash speed for the attack. The Pegasus Boots design is partially based on the Kokiri Boots Young Link wears, though with the addition of the Pegasus Boots signature wings.
The Kokiri Boots return as part of Link's Kokiri Tunic and Young Link's Standard Outfit. Unlike Hyrule Warriors, Young Link does not don the Pegasus Boots when performing his Triforce Slash-like combo and thus wears the Kokiri Boots during the attack.