Compare decoction to infusion, which is also a common way to prepare teas and tisanes. Decoctions release more essential oils and flavor from plant matter and are often used for plant matter with tough surfaces or smaller surface areas.
Leaf, flower and seed tisanes are generally made with the infusion method. Bark, root and berry tisanes are generally prepared with the decoction method.
Like "infusion," "decoction" may also refer to the beverage that results from the process of decoction.