Epiphytes are plants which grow above the ground, that grow on top of other plants. They are not planted in the soil and are not parasitic (i.e. they do not feed on other plants, however some types still damage their host in various ways). By growing on other plants, the epiphytes can reach to the light better or where they can avoid struggling for light. In plant systematics Epidendroideae is a subfamily of the orchid family, Orchidaceae. Epidendroideae is larger than all the other orchid subfamilies together, comprising more than 15,000 species in 576 genera.
Merriam-Webster Online Dictionary
epiphyte (noun) a plant that derives its moisture and nutrients from the air and rain and grows usually on another plant