One, holy, catholic, and apostolic. The Nicene Creed identifies these marks. This Creed was written to help Christians remember the essential parts of the faith. The first mark is the Church is one with the Holy Spirit.
The second mark is the Church is Holy, because the person we get our holiness from, Jesus Christ is holy. The third mark is that the Church is Catholic, meaning that the Church is universal. The last mark is that the Church is Apostolic. This is because the Church gets its tradition from the apostles.