Mat, asphalt, granules and sealant strips combine to create the basic components of asphalt shingles. As with any product, the end quality can be attributed to the quality of the components used to create it.
Mat: Shingles start with a mat foundation on which asphalt is applied. Mats have evolved over the years from pulped rags, to felt paper, and finally to the random lay fiberglass we use today, as seen below. Fiberglass based asphalt shingles do not rot and have improved fire ratings over their rag and wood ancestors.
Sealant: Sealants are special strips of asphalt adhesive that help to adhere the shingle rows (courses) together. This typically occurs during the shingle installation by heat from the sun, but cold weather installations may require the shingles to be sealed by hand. Sealants are important to help hold shingles in place during high winds, which in turn helps to protect your home against leaks.
Granules: The granules on shingles do more than just lend color to your roof. The primary function of those colored granules is to protect the asphalt from aging due to the suns UV rays. Granules come in a wide assortment of colors that are carefully blended to produce different shades, which helps them appear more dimensional.