Steep, Simmer, Salve

Hot water poured over a spoonful of dried herb and left to soak is an infusion. Roots or bark kept boiling in a pot of water for fifteen minutes or longer is a decoction. Plant-infused oil firmed up with beeswax is a salve. Each one pulls compounds out of a plant in a different way, so each one ends up holding something different and gets used differently. This site explains every preparation from the side of the person using it: what the preparation is, what's in it, how you use it, and what research has found about the method. Every article lists the studies it draws on, with links.