Grinders are a tool to help break up flower products for use. While not everyone uses these, grinders can enhance a user's smoking experience tremendously. By breaking up their flower with a grinder, the cannabis will burn more evenly and smoothly when put into a pipe. Some grinders just break up the cannabis, while other grinders have an extra feature. There is a flat surface at the very bottom, under a screen, to catch kief (what is “kief”? Maybe describe here) that falls off of the flower. After using the grinder a few times, the bottom layer can be removed and the kief can easily be scrapped to put on the top of a fresh bowl!
These are great accessories to have for anyone that uses flower pieces.