There is often confusion regarding the use of the term "Presbyterian" and the term "Reformed" or "Reformed Tradition. A rather simple way of explaining this is:
Presbyterian. The term presbyterian refers to the system of church government.
Reformed. The terms reformed or reformed tradition have to do with issues of faith or doctrine.
The Five Solas
How are we saved? "Sola fide" - By faith alone, not by church membership or sacrament.
How are we forgiven? "Sola gratia" - Byh grace alone, instead of through penance and absolution from a priest.
What is the ultimate basis of authority for spiritual life? "Sola scriptura" - By Scripture alone, above the traditions and teachings of the Roman church.
Who is the mediator of the Church? "Solus Christus" - By Christ alone. Instead of two classes, priests (mediators)and lay members, Protestants believe in One Mediator, Jesus, and a single class, "the priesthood of all believers."
What is the purpose of life and the Church? "Soli Deo gloria" - Glory to0 God alone, not to any organization, leader, or ruler.