The hair-like outgrowths that cover cannabis flowers and smaller leaves. Trichomes are where cannabinoids and terpenes are produced.
Summary from Wikipedia:
Trichomes ( or ), from the Greek τρίχωμα (trichōma) meaning "hair", are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant is an indumentum, and the surface bearing them is said to be pubescent.Read more