Cultivars are variations of a plant species that are intentionally bred or cultivated by plant growers. It could be a unique flower color or leaf variegation. Typically a cultivar is made by grafting plants or from cuttings of a mutated plant that are then further propagated until a large enough stock is available for commercial distribution. Other times they are made by hybridizing two different species or varieties. Basically, without human intervention cultivars would not exist.