The Dog Tail Cactus is an interesting piece, to say the least! This worm-like cactus is a tropical epiphyte, and requires a bit more water than traditional dessert cacti do. They are often seen climbing up and through the trees of the jungle where they are native. They can also bloom with fragrant, white flowers, but only at night.
The plant pictured is the plant for sale, and is in an 8 inch pot.