Noah's dove brought an olive leaf back to the Ark as a sign that the floodwaters had receded.
Genesis 8 describes Noah sending birds from the ark to test whether the waters had gone down. A raven is sent first, and Noah later sends a dove. On its second outing, the dove returns in the evening carrying a freshly plucked olive leaf, showing that vegetation had reappeared above the water.
The dove's return became one of the story's most recognizable images. It represents the changing conditions outside the ark and gives Noah evidence that the land is becoming habitable again. Genesis then says Noah sends the dove once more; it does not return, indicating that it has found a place to rest.
The familiar image is specifically an olive leaf, not a generic branch. Later art and popular culture often show a larger leafy twig in the bird's beak, but the biblical detail is a freshly plucked olive leaf.