*`Authorization code` - An intermediary token generated when a user authorizes a client to access protected resources on their behalf. The client receives this token and exchanges it for an access token.
*`Authorization server` - A server which issues access tokens after successfully authenticating a client and resource owner, and authorizing the request.
*`Client` - An application which accesses protected resources on behalf of the resource owner (such as a user). The client could be hosted on a server, desktop, mobile or other device.
*`Grant` - A grant is a method of acquiring an access token.
*`Resource server` - A server which sits in front of protected resources (for example "tweets", users' photos, or personal data) and is capable of accepting and responsing to protected resource requests using access tokens.
