As the number of vehicles increases, traffic accidents and waste of resources due to congestion are consistently growing every year. Cellular Vehicle-to-Everything (V2X) is a key technology improving driving safety and traffic efficiency by enabling traffic elements such as vehicles, roadside infrastructures, networks, and pedestrians to communicate with each other. Dynamic interactions between traffic elements ultimately facilitate intelligent autonomous driving. The 3rd Generation Partnership Project (3GPP) Technical Specification Group has developed a series of standards for cellular V2X features and is working on continuous enhancements for higher reliable and low latency communication. This paper provides an overview of cellular V2X use cases and 3GPP standardization, and summarizes the impact of the V2X technology.