A Canon in a church is an official. He may or may not be a priest. The Chapter of a cathedral is an official group made up of the Dean and Chapter of canons, who meet in a chapterhouse. They run the cathedral, especially the business affairs of the cathedral. They are the body which has legal responsibility for the cathedral, and for electing the (arch)bishop.
Originally, a canon was a cleric who lived in the precinct of the cathedral. The word meant a priest who was under (ruled by) a bishop.
In the Anglican church, some canons are laypersons (not ordained). The title is also given to some senior or retired priests as an honorary title.
Canon (church) Facts for Kids. Kiddle Encyclopedia.