A Tillandsia is the scientific name for what many people call an air plant.
They are members of the bromeliad family, and most are epiphytes.
Tillandsias are mostly smaller and more able to resist drought than their larger relatives. They have evolved many adaptations over time to enable them to do this.
They flower and produce seed, but they also produce small plants called offsets or pups that are attached to the parent plant. These plants often remain attached, creating big clumps of one type of plant over time.
There are several hundred types of tillandsia, ranging from extremely tiny to large, but most live off the ground, which limits their ultimate size to something that their host can bear without collapsing.