What term describes the area of the church that is about the altar, inside the chancel?

The term that describes the area of the church that is about the altar, specifically within the chancel, is indeed the sanctuary. The sanctuary serves as a sacred space where the altar is located and is often the focal point for worship and other religious activities. It is distinct from other areas of the church, such as the nave, which is the main body of the church where the congregation sits, and the chancel, which refers to the area around the altar but can include additional spaces used for specific purposes. While vestibules are entrance areas to the church, they do not relate to the altar or worship functions. The sanctuary signifies the most sacred part of the church, highlighting its importance in the context of religious practices and ceremonies.