Manual:$wgActionPaths

Details
To set 'pretty' URL paths for actions other than plain page views, add to this array. For instance:

In addition to setting this variable, you must put in place an appropriate script or server rewrite rule to handle these URLs.

unlocked magic

Spam prevention
Using $wgActionPaths, especially for the edit action seems to reduce the number of spam bots attempting article edits. It is suspected that bots are programmed to look for action=edit to identify a MediaWiki installation and act appropriately. With this in mind, it would be beneficial to name your action prefix something non-apparent so bots can't find your site when they start looking for action/edit.