API Names
Each object has an API name that is unique to the business. The API name is automatically derived from the object name, and is displayed in the object settings wizard as a read-only field.
Object Identifier
The object identifier is the primary way to interact with the API. The object identifier can be either the custom object’s API name, or the object ID.
The API name of a custom object is easily accessible in the UI when editing a custom object. Look for the read-only field “Object API Name”. This value can be used as the object identifier when using the API.