Have you heard of the money tree succulent or the jade plant? That plant is a Crassula (Crassula ovata). In the gardening landscaping world, the larger, shrub like Crassula species are frequently used as they are ultra hardy and evergreen.
There are hundreds of other Crassula species however, that collectors grow for their aesthetic appearance and beauty. Some are geometrically curious (e.g. the buttons), others have impressive spring blooms. The ornamental Crassula plants are usually showcased in pots and they tend to grow in “tower” form.