Standards are officially published or well agreed upon formats, procedures, or protocols. They allow individuals or organizations to collaborate by setting ground rules or boundaries. Standards often come with a set of preconditions or assumptions, which allow collaborators to take those conditions or assumptions as ground truth.
The concept of "standard" is at least as old as the Roman Empire, where the standard was a rod of wood often decorated with a headpiece or banner and carried at the front of an army's march. This one rod was used to establish a common length for contructing camps and buildings. By using the same length, workers constructing a door could operate independently of other workers constructing a door frame. And when the pieces were brought together, they fit.
Modern standards are often created by jurisdiction-based entities like national standards organizations (like ANSI in the USA) or the International Standards Organization (ISO).