Sacred Tradition is a term used in the Roman Catholic and Eastern Orthodox (Holy Tradition) churches that designates that special tradition of apostolic teaching handed down through the bishopric of their churches--generation after generation. Such sacred traditions are equal in authority to Scripture and comprise the totality of the deposit of faith. Sacred Tradition is considered to be inspired--just as the Bible is inspired.
In the Eastern Orthodox view, Sacred Tradition is called Holy Tradition and is that tradition handed down via the apostles from one generation to another. It does not grow and expand over time.
The Roman Catholic view of Sacred Tradition is that the deposit of faith is ever deepening and expanding with new doctrines being revealed--doctrines that have been preserved in The Roman Catholic Church throughout its history.
By contrast the Protestant position is that the Scriptures alone are the final rule of authority in the Christian church. This is known as Sola Scriptura.