C-V2X or cellular-vehicle-to-everything is a foundational technology for communication between ITS (Intelligent Transport Systems). It has been standardised by 3GPP and reference is made to existing SAE, IEEE and ETSI standards for C-V2X applications. Initially, C-V2X deployment in cars and networks will be based on LTE (3GPP Rel 14) and permit the implementation of the first safety applications. Later 3GPP releases (Rel 15 and Rel 16) will make the more complex applications which depend on very low latency and high reliability possible.