The type of name used by a gio.UnixSocketAddress G_UNIX_SOCKET_ADDRESS_PATH indicates a traditional unix domain socket bound to a filesystem path. G_UNIX_SOCKET_ADDRESS_ANONYMOUS indicates a socket not bound to any name (eg, a client-side socket, or a socket created with socketpair()).
For abstract sockets, there are two incompatible ways of naming them; the man pages suggest using the entire struct sockaddr_un as the name, padding the unused parts of the sun_path field with zeroes; this corresponds to G_UNIX_SOCKET_ADDRESS_ABSTRACT_PADDED. However, many programs instead just use a portion of sun_path, and pass an appropriate smaller length to bind() or connect(). This is G_UNIX_SOCKET_ADDRESS_ABSTRACT.
a filesystem path
an abstract name
an abstract name, 0-padded to the full length of a unix socket name