This is a jelly fungus. Jelly fungi are usually found growing on dead or dying branches.
Jelly fungi often swell when there is plenty of moisture in the air (pictured) and shrink when the air is dry. Lichen (the light greenish-grey, mossy-type growth) is also present on this branch.
While both jelly fungus and lichen can be an indicator of poor tree health, neither causes harm to the tree. Read more about jelly fungus here.. Read more on hgic.clemson.edu