Infrastructure refers to the necessary systems and facilities serving a population of people. Roads, bridges, sewers, electric grids, sewers, and water systems are all examples of "hard infrastructure" - the large physical systems necessary to sustain a modern functioning nation. "Soft infrastructure" refers to the institutions required to maintain the societal standards of their service area. Examples include the financial system, education system, healthcare system, etc.
Most often, however, the term "infrastructure" refers to hard infrastructure - especially in America, where the condition and maintenance of critical hard infrastructure has become a prominent domestic issue. As an example, more than 65,000 bridges in the U.S. are classified as "structurally deficient" and more than 20,000 as "fracture critical", according to the National Bridge Inventory. The American Society for Civil Engineers (ASCE) gave the U.S. a "D+" in its latest infrastructure report, estimating that an estimated $3.6 trillion needs to be invested by 2020 to upgrade our infrastructure.