This document, as a basis for the other parts of ISO 15118, specifies terms and definitions, general requirements and use cases for conductive and wireless High Level Communication between Electric Vehicle Communication Controller (EVCC) and the Supply Equipment Communication Controller (SECC). This standard is applicable to High Level Communication involved in conductive and wireless power transfer technologies in the context of manual or automatic connection devices. This standard is also applicable to energy transfer either from EV supply equipment to charge the EV battery or from EV battery to EV supply equipment in order to supply energy to home, to loads or to the grid. This document provides a general overview and a common understanding of aspects influencing identification, association, charge or discharge control and optimisation, payment, load levelling, cybersecurity and privacy. It offers an interoperable EV-EV supply equipment interface to all e-mobility actors beyond SECC. ISO 15118 does not specify the vehicle internal communication between battery and other internal equipment (beside some dedicated message elements related to the energy transfer). NOTE 1 – Electric road vehicles specifically are vehicles in categories M (used for carriage of passengers) and N (used for carriage of goods) (compare ECE/TR ANS/WP.29/78 ev.2). This does not prevent vehicles in other categories from adopting ISO 15118 as well. NOTE 2 – This document is destined to orientate the message set of ISO 15118-2. The absence of any particular use case in this part of ISO 15118 does not imply that it shall not be put into practice, with the required messages. NOTE 3 – This document and ISO 15118-2 are designed to work independent of data transfer medium used. However, this series of documents are made for fitting the specified data link layers in the corresponding documents in this series.