apache2.conf is the file apache looks to for initial instructions
In the installation I have the path is /etc/apache2/

The modification I have made to the default file are

1. The directory for serving site changed from /var/www/html/ to /var/www/
2. Added <virtualhost> sections to host multiple domains and sub-domains

3. The folowing was added so that php scripts would be interpreted in htm and html files
   AddType application/x-httpd-php .php .htm .html
   AddType application/x-httpd-php-source .phps
   DirectoryIndex index.html index.php index.htm