The Nutmeg tree provides a round fruit. When it is opened you will find the seed (Nutmeg) and an orange spider like spice wrapped around the Nutmeg, this is Mace. When pulled from the nutmeg seed and dried the mace is referred to a blade. The Blade can be ground to a powdered or used whole.
 
Although the flavor is similar to nutmeg it's much sweeter and more delicate in comparison. Mace is very common in North Indian Cuisine and getting more popular in the west.