Ground cinnamon is a common spice usually made from ground Cassia cinnamon rather than true Ceyon cinnamon. Look for the more pungent ground Ceylon ground cinnamon (canela) in Mexican markets or grocery stores. Otherwise the most common ground cinnamon is Cassia.
Ground cinnamon has a multitude of uses from spicing up your coffee, to sauces, many Indian dishes and it is very common used in breads and pastries in Europe. It is one of the most common spices used worldwide.
Pure ground cinnamon bark