Hi,
If no filename is specified in the url, it will automatically execute the index.php or index.html file if it exists. This is not specific to Wampserver but to Apache and it is defined by the DirectoryIndex directive in the httpd.conf file, of course, provided that the dir_module is loaded, which is done by default.
See :
DirectoryIndexIf you want to launch a file other than index.php you must add it by hand in the url.
---------------------------------------------------------------
Documentation Apache -
Documentation PHP -
Documentation MySQL -
Wampserver install files & addons