This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book brings together a collection of examples that address informal urban street markets across the globe. Experiences of the informal economy in informal urban street markets go beyond labour, production, commodities, capital, and consumption. They facilitate the learning and passing on of information and skills, generate migrant cosmopolitanisms and racism, enable the mobility and participation of both privileged and marginalized social groups, regenerate urban areas, and in some circumstances they are central to the ongoing production of society and culture. The book addresses the formation and constitution of identity, belonging, and sociality in the informal urban street market. Overall, service, governance, and policy in and for the 21st-century globalized city rarely heed Marx's exhortation to conceptualize informality on its own terms. The network of the informal urban street market becomes a territory through contingent relationships between assemblage and context.