The type friend is both user and peer type.
Found this somewhere:
* peer: A SIP entity to which Asterisk sends calls (a SIP provider for example). If you want a user (extension) to have multiple phones, define an extension that calls two SIP peers. The peer authenticates at registration.
* user: A SIP entity which places calls through Asterisk (A phone which can place calls only). Users authenticate to reach services with their context.
* friend: An entity which is both a user and a peer. This make sense for most desk handsets and other devices. Asterisk will create two objects, one peer and one user, with the same name.