According to ASME: A standard is "a set of technical definitions and guidelines, “how to” instructions for designers, manufacturers, and users. Standards promote safety, reliability, productivity, and efficiency in almost every industry that relies on engineering components or equipment."
Compliance with standards in the design process is voluntary for companies, however, it may become mandatory if written into contractual business obligations and/or adopted by federal, state, or local regulations. Also, market conditions encourage many companies to comply with standards, even in cases where they are not mandatory.
It is important to have a general idea of the published standards that may impact your project early in the design process, when requirements are being established. You may dive deeper into standards during the detailed design phase.