If you are actually inquiring about a plant that partially fits this description (and not dyed, preserved hydrozoans which are often marketed as "air ferns"), you have probably encountered a member of the genus Tillandsia which belongs to the pineapple plant family, Bromeliaceae. Most Tillandsia species are epiphytic, using their root systems for anchoring to trees or rocks, while absorbing nutrients and moisture through their leaves. While this lifestyle works perfectly fine in their natural habitats, you will probably be unsuccessful in maintaining these species (also erroneously known as "air plants" or "air ferns") over the long-term without supplemental water or fertilization. If you are interested in maintaining members of this diverse and attractive plant genus in your home, basic husbandry information can be found online. Just look under something like "Tillandsia care".