This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book builds on the SACN's project to increase understanding of South Africa's secondary cities and contribute to today's policy debate. Urban research in South Africa is largely dominated by work on Cape Town, Johannesburg and Durban, with the problems of the secondary cities and regions of urban systems being largely ignored. The complexity of settlement classification in South Africa is evident from, among other policy documents, the Urban Development Framework and the White Paper of Local Government. Government legislation divides municipalities in South Africa into three categories: metropolitan municipalities, local municipalities and district municipalities. The Council for Scientific and Industrial Research (CSIR) conducted its first research on the South African spatial economy in 2008. The 'unbalanced' economic development, together with the apartheid regime's prioritisation of 'homeland' development, led to policies of influx control, growth point development and industrial de-concentration.