The word `kif` is derived from Arabic `kayf`meaning well-being or pleasure. Kief, keef or keif is a fine powder made from dried resin glands (trichomes) that are found on the leaves of the cannabis plant. It contains a high concentration of the psychoactive chemical or THC that causes euphoric feelings or opium-like high that can last for hours. Kief is also called crystal or pollen. The quality of keif depends on the quality of marijuana plant. Read a detailed article on Kief on Cannabis Culture here.
Grinders can be found in various sizes, shapes and made of different material. Which one would be the best for your needs depends on how much money you are ready to spend and also on how often you intend to use them. Grinders are made of plastic, wood, acrylic and metal. They can be electric or manual. People say that they collect different amounts of kief with different grinders.