It refers to the fundamental facilities and systems serving a country, city, or area, including the services and facilities necessary for its economy to function. It typically characterises 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.
Land improvement and land development are general terms that in some contexts may include it. But in the context of a discussion of it would refer only to smaller scale systems or works that are not included in it. Because they are typically limited to a single parcel of land, and are owned and operated by the land owner. For example, an irrigation canal that serves a region or district would be included with infrastructure. But the private irrigation systems on individual land parcels would be considered land improvements, not infrastructure. Service connections to municipal service and public utility networks would also be considered land improvements, not infrastructure.