The part of the church where the people gather before mass

Where the sacrament of baptism occur

where the sacrament of Reconciliation occurs in a church

Where the consecrated hosts are kept in the church

Where the sacred chrism is kept (chrism is the oil used in the sacrament of Confirmation)

A cathedral, is named for the "cathedra". The cathedra is:

This structure is sometimes found in cathedrals. Walking through it symbolizes traveling on a pilgrimage. It's also used as a way to focus while you pray or meditate.

These are side rooms that people use for personal prayer when at the cathedral.