OAuth Terminology

Access Token
A value used by the consumer to gain access to protected resources on behalf of the user, instead of using the user’s Salesforce credentials. The access token is a session ID, and can be used directly.
Authorization Code
A short-lived token that represents the access granted by the end user. The authorization code is used to obtain an access token and a refresh token.
Connected App
An application external to Salesforce that uses the OAuth protocol to verify both the Salesforce user and the external application.
Consumer Key
A value used by the consumer—in this case, the Mobile SDK app—to identify itself to Salesforce. Referred to as client_id.
Consumer Secret
A secret that the consumer uses to verify ownership of the consumer key. To heighten security, Mobile SDK apps do not use the consumer secret.
Refresh Token
A token used by the consumer to obtain a new access token, without having the end user approve the access again.
Remote Access Application (DEPRECATED)
A remote access application is an application external to Salesforce that uses the OAuth protocol to verify both the Salesforce user and the external application. A remote access application is implemented as a connected app. Remote access applications have been deprecated in favor of connected apps.