Crowd work, also known as crowdsourcing, has emerged as a disruptive force in the labor market. It involves sourcing work from a large pool of individuals, often over the internet which is referred as digital labour platform, and has gained popularity due to its potential to reduce costs, increase speed, job autonomy, and improve quality of work. Though Crowd work creates lots of job opportunities, still a lack of regulatory framework is setting back people to evolve as a crowd worker. This paper provides a comprehensive review of the literature on crowd work, examining its history, key concepts, and current state of research. The paper also identifies opportunities, challenges, and implications for the future of work.