A standard is a "document that provides requirements, specifications, guidelines or characteristics that can be used consistently to ensure that materials, products, processes and services are fit for their purpose." (ISO, 2013) Standards that are incorporated into law or government regulations are often referred to as codes.
Standards apply to everything from paper towel dispensers, low voltage fuses, implants for surgery using acrylic resin cement and to iron and steel products.
Standards are typically reviewed every 5 to 7 years. Check the standards's body's website on a particular standard. They should have some information about how current a standard is, and whether or not it's still in effect.
Standard numbers may include some or all of the following information, appearing in order from left to right (e.g., ISO/IEC 8859-1: 1998):