Yardstick is a term which comes from yard and stick. So, the term means a stick which can measure a yard. Yardstick is now an accepted buzzword in strategy / marketing / business, and is used in competitive analysis / benchmarking; it is used metaphorically as a measuring tool.
Example: What is the yardstick by which we measure employee performance in this company? Loyalty, hard-work, team-spirit!