It depends on the church.  They support the Pasor in his duties basicly.  They usually fill in the pulpit when pastor is gone, they assist with church issues that the pastor can not attend to for one reason or antoher.   I would look at the churches constitiution to see if there are spesified duties.  They should also be an unbiased advocate fro the flock/pastor.  IE if they see somthing not right they need to say somthing to whichever party.