preface: I'm new to web servers and scripting.

what is the control flow of the fastcgi to nginx boot sequence?
both the fast_cgi configuration file and the nginx configuration file have
$variable assignments, what is the original instantiater of these variables?




context for question:

i notice there is an "emerg" component that is unhappy with my configuration
file, and the source code suggests it's with one of my variables with the
ngx_http_variables code,
the exact message was "unknown "query" variable" now I have resolved it
(interestingly enough I have no "query" variable (maybe its the default no
time for inspection now),
however the first fast_cgi param was "$query-string" (also new to this
"fastcgi")), with this context, this leads me to my open question....

both the fast_cgi configuration file and the nginx configuration file have
$variable assignments, what is the original instantiater of these variables?

Magdalena