Infrastructure refers to structures, systems, and facilities serving a country, city, or area, including the services and facilities necessary for its economy to function. It typically characterizes technical structures such as roads, bridges, tunnels, water supply, sewers, electrical grids, telecommunications, and so forth, and can be defined as "the physical components of interrelated systems providing commodities and services essential to enable, sustain, or enhance societal living conditions.
Infrastructure may be owned and managed by governments or by private companies, such as sole public utility or railway companies. Generally, most roads, major ports and airports, water distribution systems and sewage networks are publicly owned, whereas most energy and telecommunications networks are privately owned. Publicly owned infrastructure may be paid for with taxes, tolls, or metered user fees, whereas private infrastructure is basically paid for by metered user fees. Major investment projects are generally financed by the issuance of long-term bonds.
Hence, government-owned and -operated infrastructure may be developed and operated in the private sector or in public-private partnerships, in addition to the public sector. The lack of infrastructure in many developing countries represents one of the most significant limitations to economic growth and achievement of the Millennium Development Goals. Infrastructure investments and maintenance can be very expensive, especially in such areas as landlocked, rural and sparsely populated like Africa and Asia.