Protection policy is used by wiki administrators to prevent vandalism. Frequently viewed pages (such as the main page) are usually protected from being overwritten by any uploads.
There are four types of protection: full, semi, move, and cascading.
Full protection prevents any unauthorized edits.
Semi protection stops anonymous and accounts less than four days old from editing.
Move protection guarantees the page won't be renamed.
Cascading protection keeps content from transcluded pages safe.