The Series 66 exam is a licensing test for individuals seeking to become investment adviser representatives and securities agents. It combines elements of the Series 63 and Series 65 exams, covering topics such as investment products, regulations, and ethical practices. Passing the Series 66 allows candidates to work in multiple states without needing to take additional exams. The exam is administered by the Financial Industry Regulatory Authority (FINRA) and consists of 100 multiple-choice questions. Candidates must achieve a passing score to obtain their license, which enables them to provide investment advice and manage client portfolios effectively.