The term "our Lady" has been added to the Catholic Gospel.
There is no "our Lady" in the New Testament, only "our Lord."
This lady is presented as being a perpetual virgin, of perfect
birth herself. She is said not to have had children, despite
the bible suggesting she had at least eight of them. She
ascended to heave (I think) and sits on the right hand of
Jesus.
So the priest is the parishioner's mediator with Mary, who is
the mediator with Christ, who is the mediator with God.
People get confused when I say I don't know much about
the Catholic Church. "But you are religious, you read the
bible!" And here's the point - all this Mary stuff isn't really
in the bible - it's all man-made.
Well you certainly don't know a great deal about Catholic belief, as you have just demonstrated. There seems little room for confusion there.
There is no "Catholic gospel". What are you referring to?
And the priest is not an intermediary between parishioners and Mary. He is an intermediary, for certain specific (sacramental) purposes, with God.
And it is also nonsense that Christ is a mediator with God.* Catholics believe in the Trinity.
[* Erratum note: Windwalker has subsequently point out to me that I was incorrect here: the bible actually does speak of Christ being a mediator between God and Man, having both human and divine nature himself.]
Mary is one of the saints, the most important, being the Mother of God. Catholics sometimes pray to the saints to intercede with God for them, as well as to God directly. Due to her importance, and the fact that she is an archetypal mother figure and thus seems particularly approachable, there are quite a lot of prayers to Mary in the Catholic church.
It is quite true that a lot of Catholic theology is not found directly in the bible. Some of it is the product of the thought of theologians and holy men and women through the centuries, reflecting on scripture. But then this is just what any Protestant preacher does, interpreting bible passages for his flock, in the pulpit on any Sunday. The difference is that the Catholic church, being old and having a culture of learning, has collected a number of these interpretations and adopted them formally as part of the beliefs.