DBusWatch function, DBusTimeout functions Why these functions is needed ?

Hi All,

Currently I have faced with understanding of watch and timeout functions in
libdbus.
I do not quit understand why they are needed.

From description I understand they are needed to check state of socket. If
something changes then from libdbus I will receive this message and I have
either to read something or to write something to socket.

It means that I should not create infinite while loop, but register
callbacks and when will be possibility I will write to out-queue or read to
in-queue, am I right ?

And maybe some brief explanation what is DBusTimeout function ?