Canela is the Spanish word for cinnamon. This cinnamon used in Mexican cooking is the softer loose-bark variety grown in Ceylon rather than the more commonly found hard-stick cinnamon. Canela is easily ground in a molcajete or other mortar and pestle (including your electric coffee/spice grinder).
You can find canela in most any Mexican market or some specialty stores. You may also purchase it online at Amazon.com.