is a large genus of relatively easy-growing succulent stemmed plants, ranging from tiny little plants to large tree-like species. The species in South African is commonly referred to as "Naboom and noors" in Afrikaans. It is a widespread genus, known from the Americas, Asia, Africa and Madagascar. The greater concentration of succulent species is known from Africa and Madagascar.
The variability in the genus presents an array of plant forms, sizes, leaf shapes, colours and textures.