Blocking users is an action that administrators can perform upon users or IP addresses to prevent them from editing the wiki.
Blocking users is fairly straightforward: visit Special:Block and follow these steps:
To unblock a username or IP address, go to the active block list and click on the (unblock) link next to the user or IP you wish to unblock. Then, enter in an optional reason and click on the unblock button. A message should appear saying if the unblock was successful or unsuccessful. Alternately you can go directly to the Special:Unblock page and manually enter the username or IP address to unblock.
Blocked users are unable to edit pages, upload files or move pages. Effectively, this makes the wiki read only for those users. Note that administrators with access to the blocking and unblocking interface may still block and unblock others (including themselves) while blocked.
If a blocked user tries to edit a page or perform another blocked action they will see a message informing them that they are blocked, how long the block is in effect for, who applied the block, and the reason for the block if one was provided.