Terminology for keys
In Microsoft Dynamics AX, an AOT node under MyTable > Relations represents a foreign key.
A key whose value has meaning to people. Most replacement keys are natural keys.
A key whose value has no meaning to people. A large number generated by the system, such as RecId, could be a surrogate key.
A broad term that applies to primary keys and to alternate keys. It does not apply to foreign keys. This term emphasizes that all values for a given key must be unique within one table. All fields in a unique key must be not-nullable.