A more thorough explanation:

Dioichia is a district where a bishop carries out his religious duties.

• The bishop of Rome is responsible for the dioichia of Rome.
• The dioichia of New York is overseen by the bishop of New York.

These examples show that dioichia refers to a specific area where a bishop has authority over the spiritual needs of the people living there. Just like how a mayor has jurisdiction over a city, a bishop has jurisdiction over a dioichia.