Standards can be mandatory or voluntary.
Think of standards as rules for uniformity, size, quality, performance, shape, definition and testing methodology of manufactured products. Specifications are concise statements of requirements for materials, products or services that are to be purchased by an industry or government agency. Specifications are limited to a project or agency. Standards are specifications that are recognized as the most practical and appropriate current solution, that is agreed upon by a recognized authority, for a recurring problem. Most standards are created by professional societies or governmental organizations.