"A standard is an agreed way of doing something in a consistent and repeatable way. Standards set minimum requirements in terms of safety, reliability, efficiency and trust." (IEC)
Standards often supplement the design process by guiding the engineer, saving significant design time. They are updated frequently to keep pace with changing technologies. Usually, you want to ensure you're looking at the latest version of a standard; however, older, superseded versions of a standard may be useful in many cases, especially when evaluating a product or process created when the old standard was in place.
Standards are created by a variety of organizations and may be voluntary or legally mandated. Examples of organizations that develop standards include the CSA Group in Canada or the International Organization for Standardization (ISO). These organizations will facilitate the process of developing a standard, but the standards themselves are written by committees or working groups of experts with subject knowledge and an interest in developing the standard.
You might also encounter different terms such as guidelines, codes and regulations. The differences are related to whether or not the document is mandatory or voluntary. A standard is voluntary. This means it should be followed, but if it isn't then there are no legal consequences. A guideline is also a recommendation. Codes, however, are requirements that must be followed.
Some examples of Standards and Codes include:
UBC Library has a Standards Guide listing some common standards organizations and where to find their standards.
When searching for a standard enter the document number or title keywords to find the standard you need.
Elements of a Standard. The following video from McMaster University Library describes reading through a standard in some detail.