Infrastructure was the basic physical and organizational structures and facilities needed for the operation of a society.
Following the Monean discovery of the Waters in the mid-21st century, the otherwise nomadic people settled therein after the found that they could farm sea vegetation and extract oxygen from the ocean for their ships. By the 24th century, they had further built an industrial infrastructure, which included industrial complexes, and undersea dwellings. (VOY: "Thirty Days")
Harrad-Sar claimed, in 2154, to have discovered a planet with large deposits of magnesite, because he did not have the infrastructure he needed to get the magnesite out of the ground, he wanted Starfleet to construct mining facilities in exchange for a ten-percent share. (ENT: "Bound")
After the USS Enterprise was thrown into System J-25 in 2365, scans of the fourth planet there indicated that it possessed a system of roads, which indicated a highly industrialized civilization, but where there should have been cities, there was only great rips in the surface. (TNG: "Q Who"}
Prior to departing Gaia in 2373, Worf made a survey of the infrastructure of the main settlement there so that the USS Defiant could leave behind the appropriate supplies. (DS9: "Children of Time")
During his investigation of Hogan's remains, which included his partial uniform, the Voth molecular paleontologist, Professor Forra Gegen, assumed that the person whose remains he found was part of a social infrastructure, which in turn implied he was the member of a starship crew. (VOY: "Distant Origin")
When the Ledosians were inadvertently granted access to Ventu territory, they immediately conducted an expedition where they made scans to evaluate the potential for anthropological research and resource development of the once off-limits habitat. As for the Ventu themselves, the Ledosians intended to help them with better opportunities, through the introduction of medicine, infrastructure, education, and technology. (VOY: "Natural Law")