Carbon dots gets more attention in recent days and several research articles reported that the carbon dots are highly promising material in carbon based nano materials. The discovered zero-dimensional carbon dots have unique physical and chemical properties due to good quantum confinement and small size (<10 nm). Organic macromolecules with large size involved in the thermal carbonization process and formed Carbon dots. Variety of bio-natural carbon sources can be used for the synthesis of carbon dots by various methods such as hydrothermal, microwave, laser ablation, electrochemical methods, ultra-sonication, chemical oxidation etc. Carbon dots have outstanding properties, such as water solubility, low toxicity, good surface passivation and functionalization, comparable optical properties etc. The unique and fascinating properties of these carbon dots attracts the researchers more to show significant interest in various field such as sensing, photocatalyst, supercapacitor, bioimaging etc. This comprehensive chapter aims to supply the reader with a broader perspective of carbon dots by the concept of synthesis (using various biomass as a precursor) and multifarious applications of carbon dots like metal sensing and photocatalytic process.