Why are there 2 types of cinnamon and what is used to make one kind hot?

Answer 1

Cinnamon is cinnamon. Some of it is hot because the oils have been boiled and concentrated.
There is only one cinnamon. It comes from a tree bark.

Answer 2

The two types you mention both come from the bark of tropical evergreen trees,belonging to the cinnamomium species.Cassia is the bark of Cinnamomium cassia,major producers are China & parts of India,the true cinamon or quills as that form is referred to comes from the tree Cinnamomium verum,this after drying curls into a tight roll unlike the thick,flaky rough surface of cassia.Cassia is relatively pungent due to it's essential oils & is therefore used in spicy cuisine like curries.Cinnamon is used to flavour various dishes typical to various regions of the world,it flavours items like coffee,apple pie & apple strudel typical dessert of austria,it is part of spice powders like Indian Garam masala as well as the chinese five spice powder.Cassia is used where pungency is needed.