configure part of installing apache

[Andrew Critchlow <a_critchlow@hotmail.com>]

Configure part of installing apache
 
Hi eveyone, I am desperate need of help to understand the configuration when using ./configure to install apache 2.
 
./configure --prefix=/usr/local/apache --enable-so
I understand what the prefix does, its the module theory.
>From my understanding --enable-so, enable shared objects.
So correct me if i'm wrong I can now, in the httpd.conf load a module via, for example:
LoadModule php5_module        modules/libphp5.so

But then there are commands such as:
--add-module=module_type:/path/to/3rdparty/mod_foo.c --enable-module=shared
&
--enable-module=shared
What do each of these do?
Why would I ever need this if I have used --enable-so ?
I installed PHP using ./configure --enable-so and everything worked fine.
 
Also where does apxs come into it all?
When I configured PHP I used:
./configure --with-apxs2=/usr/local/apache/bin/apxs
I don't really understand what this means?
 
 
 
Many many thanks to anyone who can help with this!
 
 
 
 
 
 
Andrew.