The infrastructure is the basic foundation or underlying framework of an organization or system. In your house, the infrastructure is the system of beams, weight-bearing walls and the foundation that keeps it standing.
Infrastructure often refers to the equipment and structures required by the military or by a country or region. Roads, bridges, and school buildings are part of our nation's infrastructure, and are necessary for the continued growth of our communities. This word was formed as a compound in English, using the prefix infra- "below, underneath."