Asphalt shingles come in two basic types: glass fiber (a.k.a. fiber glass) and organic.
Organic shingles consist of an organic felt material which is generally paper saturated with asphalt to make it waterproof. A top coating of adhesive asphalt is then applied and the ceramic granules are then embedded. Organic shingles contain around 40% more asphalt per square (100 sq. ft.) than their glass fiber counterpart which makes them weigh more and gives them excellent durability and blow-off resistance.
Glass fiber shingles have a glass fiber reinforcing mat manufactured to the shape of the shingle. This mat is then coated with asphalt which contains mineral fillers. The glass fiber mat is not waterproof by itself. It’s purpose is for reinforcement. What makes the glass fiber shingle waterproof is the asphalt. However, the asphalt itself will not stick to the mat. For this reason, “fillers” are used. The fillers in the asphalt cling to the glass fibers in the mat. The asphalt then encapsulates the glass fibers, fills all of the little holes and voids in the mat rendering it waterproof. After this cools a bit, an adhesive asphalt is used to cover the mat and the ceramic granules are then embedded.