Plants and herbs consumed by humans are the rich sources of phytonutrients compounds synthesized in plants itself. Such bioactive substances are responsible for the plant’s antioxidant and medicinal values. Flavonoids are an essential group of naturally occurring polyphenolic compounds, and its flavan nucleus characterizes it. It is one of the most common classes of compounds available in vegetables, fruits, and plant-derived beverages. Flavonoids are considered as health promoting and disease preventing dietary supplements. It is now considered as an indispensable component in a variety of nutraceutical, pharmaceutical, medicinal, cosmetic and other applications. Objectives: The main aim of this present review is to discuss the current trends of research and development on flavonoids, general working mechanisms of flavonoids, functions, and applications of flavonoids, prediction of flavonoids as potential drugs in preventing many chronic diseases and future research directions. Discussion: Their basic structures consist of C6-C3-C6 rings with different substitution patterns to produce a series of subclass compounds such as flavones, flavonols, flavanones, isoflavones, flavanols or catechins and anthocyanins. Many flavonoid compounds are shown to have an antioxidative activity, free radical scavenging capacity, cardioprotective, antidiabetic, anti-inflammatory, anti-allergic while some other flavonoid compounds exhibit potential antiviral activities. More recently flavonoids are proven to be the most effective as an anti-cancer agent, through apoptosis by induction of cell cycle arrest and inhibition of key enzymes involved in tumor promotion.