Carbon Quantum dots are a class of materials studied under Nanotechnology. We know that nanotechnology is a wide research topic as it has wide range of applications in various fields. This review is about carbon quantum dots which is the carbon material in the range 1-10 nm. Carbon Quantum dots with unique optical properties, low toxicity, low cost and simple synthetic routes are very important research topic in coming decades. CQDs have 2 approaches for fabrication top-down and bottom-up. CQDs are also known as fluorescent carbon nanoparticles. In this review we have discussed the information about carbon quantum dots, their synthesis, properties and also their wide range of applications in various fields like optronics, bio medicine, and sensors etc. which are helpful for future generations. This review summarizes the research, application and brief study of carbon quantum dots.