The word keif comes from the Arabic word kayf, meaning pleasure or intoxication. Basically, it is the resinous trichomes that collects after cannabis buds are sifted either through a grinder or sieve.
Kief is a powder loaded with THC, the psychoactive property in cannabis. Traditionally, kief is the basis of hashish. The fine powder is often pressed into cakes of hash and can then be smoked or vaporized. If you tried hashish in your younger days, you’ve had kief.