This Supplement will take as a start point four components of digital transformation for people-centred cities and communities: data, people, digital technologies and their interrelationships. It will then analyse different terminologies, concepts, keywords and attributes around the 'people-centred' concept. Such an analysis of the definition of digital transformation, is helpful not only for understanding the tasks of digital transformation, but also for carrying out concrete work in the aspects of information and communication technology (ICT) infrastructure, key performance indicators (KPIs), stakeholders and strategies, for what ITU considers as smart sustainable cities.