Global cities are defined as primary nodes in the global economic network that serve as important hubs for business, finance, trade, and globalization. The document discusses the key traits of global cities, including international financial services, multinational corporate headquarters, major financial institutions and stock exchanges, domination of surrounding trade and economies, manufacturing centers and ports, decision-making power, innovation centers, media and communication hubs, highly educated populations employed in services and information sectors, and infrastructure and facilities that support legal, medical, and entertainment industries. It also outlines GaWC's classification of global cities into Alpha, Beta, Gamma, and Sufficiency categories based on their degree of integration and connectivity within the global economy.