An administrator can change the following settings in Settings > Site administration > Server > HTTP.
Use slash arguments
You will need to change this setting only if you are having trouble viewing files or images. Most of the time, Moodle will display files and pictures with no problem using the slash arguments. If you get errors when you try to view pictures or files from within Moodle, your PHP server doesn't allow the slash argument method and you will need to disable this setting.
Observe that if you disable slash arguments then you no longer can have file resources with multiple files and relative links in between them (e.g. web pages, c.f. MDL-19334).
Proxyhost and proxyport
Your Moodle server may need to access the Internet through a proxy server, depending on your network configuration. If you're not sure about whether you need a proxy server, contact your network administrator or ISP.