The resource identifier portion of a Jabber ID provides further specifying information about a node or user, for example by identifying the location from which a user is connecting (e.g., home or work), the type of device a user is connecting with (e.g., notebook or handheld), or a user's specific Jabber Client.

See Identifier

An integer that uniquely identifies a resource among all of the other resource of the same type in a resource database. The resource identifier is chosen by the application programmer, and remains constant.

a URI plus an optional anchor ID