"The use of loadable modules to enable optional features is one of the nice things about Apache. This makes memory management much more efficient than it would be if all of these features were compiled in with the Apache code. This way, if you need a certain feature, just enable the module that goes with it. If you don’t need the feature anymore, just use the “a2dismod” command to disable the module, restart Apache, and the memory that that module had used will be released for other purposes.
"If you look in the /etc/apache2/mods-available directory, you’ll see that there are a lot of other modules that do come with Apache. Not all of them are enabled.
