In Logic, Appeal to Authority is an informal fallacy of weak induction. This fallacy occurs when someone uses the testimony of an authority in order to warrant their conclusion, but the authority appealed to is not an expert in the field in question.
For example, if someone said, “Einstein said ‘God does not play dice with the universe,’ therefore God must exist.”
In this argument the fact that Einstein seems to believe in God is used as evidence for the existence of God. However, Einstein is an expert in Physics, not Philosophy or Theology. Therefore, the “authority” of Einstein is not sufficient to provide evidence for the truth of the conclusion.