Help:System messages

System Messages 

Systems Messages provide a means for customising the look and feel of a wiki. Because their impact is system wide only admins and above normally have access to them. Others may look, but they may not edit.

Appearance
Monobook.css - The global stylesheet for your wiki. Monobook.js  - ?

File Management
1movedto2 1movedto2_redir

These relate to the renaming of files, which is done by moving a file from one name to another.

Headings
These only affect the page headings of certain messages that are displayed to users when they have done something.

addedwatch - This shows up anytime a logged in user adds a page to their watch list.

Message Texts
Why would you want to muck with these messages? Probably you wouldn't. Exceptions would be to improved readability from the standpoint of your target audience. Particularly if you expect them to be accustomed to a language different from the defaults.

addedwatchtext - Text to be displayed when a user has chosen to watch a new page.

From Wikia, a Wikia wiki.