Summary excerpted from Learntarot.com
because I am too lazy to type my own right now:
Except in rare cases, every human grows and develops within a culture. We learn by living with others. The Hierophant represents such official learning, especially in groups. A Hierophant is someone who interprets secret knowledge. On Card 5 we see a religious figure in a formal church setting. He is wearing the elaborate vestments of his office. His task is to bring the two initiates into the church so they can take up their appointed roles.
Besides churches, there are schools, clubs, teams, companies, and societies. The Hierophant represents all of these because his realm is structured groups with rules and assigned roles. Such environments emphasize belief systems - facts, rules, procedures, and ritual. Members are rewarded for following conventions. They develop a group identity.
In readings, the Hierophant often represents learning with experts or knowledgeable teachers. This card also stands for institutions and their values. The Hierophant is a symbol of the need to conform to rules or fixed situations. His appearance in a reading can show that you are struggling with a force that is not innovative, free-spirited or individual. Groups can be enriching or stifling, depending on circumstances. Sometimes we need to follow a program or embrace tradition, other times, we need to trust ourselves.