For example, all plants can be put in order from the more primitive to the more advanced. Small with leaflike, stemlike, and rootlike structures. Larger with true leaves, stems, and roots. Ferns, horsetails, club mosses. This informal way of describing plant classification gives an overview of how plants are classified.
Botanists use a more complex system.
A botanist divides the plant kingdom into Divisions, similar to the Phyla used to divide the animal kingdom. There are twelve divisions. Put somewhat simply, individuals in a species are able to breed with each other, while in broader categories individuals do not interbreed. The foxglove plant is the source of digitalis. Photo by Steven R. King, 1996.