If you signed up to use any web hosting service, you're more than likely on a shared host, unless you specifically signed up for a (more expensive) dedicated host. The difference is that many accounts will be hosted on one shared server, whereas if you signed up for a dedicated server, then only your account is on that server (and thus you could have access to server-wide configuration items).
For many configuration items, if you're on an Apache server you can customize the settings within a .htaccess file in your web root directory. Whether you actually need to change any such settings for whatever you want to do is a whole different question.