Cactus are succulent plants, primarily native to the Americas, adapted to arid and desert-like environments. They are characterized by thick, fleshy stems that store water, modified leaves that often appear as spines, and an overall waxy coating to minimize water loss. Cacti come in a wide variety of shapes and sizes, including columnar cacti with tall, straight stems and prickly pear cacti with flat, fleshy pads.