Creeds express and make clear the most important Christian beliefs, including about the nature of God. The congregation often recites them during acts of worship, usually standing.
The creed that is recited in Mass on a weekly basis will usually be the Nicene Creed. Within the creed, the nature of the Church is made clear in the final verse -
I believe in one, holy, catholic and apostolic Church.
This is the sole Church of Christ, which in the Creed we profess to be one, holy, catholic and apostolic. These four characteristics, inseparably linked with each other, indicate essential features of the Church and her mission.CCC 811 (Catechism of the Catholic Church)
The words one, holy, catholic and apostolic are often called the four marks of the Church.