Goddess Crest

The Goddess Crest is a recurring symbol in SS undefined that represents the goddess Hylia, appearing throughout many Temples from the era in which she was in power. The predecessor to the Wingcrest and the Hylian Crest, it has multiple functions, all of which are activated by a Skyward Strike. Other, more bird-like variations of the crest can be found throughout Skyloft, including on Zelda's clothing.

Temples and the Ancient Tablet
Glowing, levitating Goddess Crests are found in the Statue of the Goddess in Skyloft, Skyview Spring in Skyview Temple, the Earth Spring in the Earth Temple, and the Isle of Songs. Triggering the first with a Skyward Strike raises the altar on which the Ancient Tablet is to be assembled, while the second and third grant recorded messages from Hylia and access to the Ruby and Amber Tablets. The fourth is used in the quest for the Sacred Flames.

Goddess Cubes
Goddess Cubes are cubes of an unknown metal with the Goddess Crest embossed on them. A Skyward Strike converts them to a beam of light that shoots into the sky and activates a corresponding Goddess Cube Chest.

Goddess Wall
The Goddess Crest also sometimes appears on the walls of Dungeons. Charging up a Skyward Strike and then drawing the form of a consumable Item (e.g. Hearts, Rupees, Bombs, Arrows) where the symbol is will lead to that Item appearing. Drawing the Triforce will produce Fairies.

Theory
Preceding its various Loftwing-inspired variations, the Goddess Crest lacks bird-like features except for wings. Because it is the symbol of of the goddess Hylia, who is almost always symbolised as having had angelic wings, it is possible that the original Goddess Crest alone is depicting Hylia herself, meaning that the future Hylian Crest and Royal Crests are a combination of both Hylia and the Loftwings.