Which address is correct?
A customer’s address may appear in an account system, a CRM, and a support tool. If the addresses differ, the team chooses a trusted source, perhaps the account system, and uses it to correct the others.
A system of record is the system responsible for keeping a particular fact current. Other systems may keep copies, but need to know where updates should come from.
One source for each fact
An account system may own addresses, while a billing system owns payment history. There is rarely one source for everything. Teams document who may change each fact and how updates reach other systems. Historical reports may still show an earlier value on purpose.