Moss is a type of plant that does not have traditional roots, stems, or leaves. Because they have no true roots, mosses use delicate growths called rhizoids to anchor them to soil, rocks, or tree bark. Moss grows along the ground where it is moist, absorbing water and nutrients from the air.
Like their cousins the ferns and liverworts (leafy mosses), mosses reproduce from spores, not seeds, and need to be moist in order to reproduce. They grow in soft cushions or small clumps, and can spread out like a blanket along the ground.