This is a good example of an Alpine Garden. Alpine gardens are created to represent miniature Alpine landscapes. And often to help create a more authentic realistic look, small rocks miniature plant varieties are used.
This design is very creative, placed well, and realistically represents a mountain slope. It only stands to reason that these type of rock gardens are often created to landscape slopes and hillsides.
Another element that helps create an authentic and consistent feel is for the rocks to be from the same lot or to be close to the same in appearance. This design has a few variations but is mostly all the same type of rock.
The plant selection in this small alpine rock garden is mostly miniature, moss, and even some dwarf pines. See growing moss on rocks to discover how you can grow your own moss for your garden design.