What is the difference between the API Key and the Consumer Key?
The terms API Key and the Consumer Key both refer to the same OAuth key, which the official OAuth spec calls the Consumer Key. The term API Key, however, is widely used when referring to keys for Web APIs. Thus, OAuth Applications use the term API Key, while Open Applications adopt the official OAuth term. The YOS documentation uses the term consistent with the type of application (Open or OAuth) and parenthesizes the equivalent term.