What did a medieval cardinal do?

A medieval cardinal served as a senior official within the Catholic Church, often acting as a key advisor to the pope and holding significant authority in church governance. Cardinals were responsible for electing new popes, managing church affairs, and overseeing dioceses and other ecclesiastical institutions. They also played crucial roles in diplomatic missions and resolving theological disputes. Additionally, many cardinals held significant wealth and power, influencing both religious and secular matters in their regions.