Flavonoids are secondary metabolites in large amounts in plants, fruits, and seeds. Flavonols are found in a variety of plants, including fruits, vegetables, herbs, spices, aromatics, and medicinal plants. In addition to having antioxidant properties, flavonoids have immunomodulatory properties, anti-inflammatory properties, and anticancer properties as well. In this review, we discuss the chemistry, classification, sources, flavonoid extraction methods, stability, and biological activities of bioflavonoids.