Sede vacante is an expression, used in the canon law of the Catholic Church, that refers to the vacancy of the episcopal see of a particular church. It is Latin for "the seat being vacant", the seat in question being the cathedra of the particular church.
At this moment, the Diocese of Sault Ste. Marie is without a Bishop, after Bishop Marcel Damphousse was appointed the new Coajutor Archbishop of Ottawa-Cornwall.
Until the Holy Father Pope Francis appoints a new Bishop for the Diocese of Sault Ste. Marie - the administration of the Diocese is left into the hands of a temporary administrator elected by the College of Consultors - a committee of priests who usually have the responsibility to consult with the Diocesan Bishop about the life of the local Church.
You will notice, during this time, that during the Eucharistic Prayer at Mass, the priest will no longer mention the name of the Bishop, simply saying "together with Francis, our Pope, and all the clergy", until the time of an appointment of a new Bishop of the Diocese.
Please pray that the Holy Spirit will select a great Bishop for the Diocese of Sault Ste. Marie.