about signals

we are now going to develop a system using PostgreSQL on Linux.
this is the first time for us to use PostgreSQL , as well as Linux.
many things we would like to ask...

this time, the question is about SIGNALS.
I know there are some signals used for the interactions between
postmaster and backend(DB server). but not the details.

for example,
think of the case when you make PostgreSQL-included programs used as
LIBRARY.
if a signal occured at PostgreSQL-process when other apllication is applying
to that
LIBRARY, does this application catch that signal (from PostgreSQl) in
mistake for the one
from its child process??
we would be much pleased if you help us about this question.

we need more detailed information about how they work.
the info about where we can get answers is pleased, too.

and this is rather urgent.
I do waiting for your reply!!!