Ignore lists are used for those people whose messages you wish not to read. By adding someone to your ignore list, those messages posted by these individuals will be hidden when you read a thread.
If there are particular members that bother you and you do not want to see their posts or receive Private Messages and Emails from them, then you can add these members to your 'Ignore List'. There are several ways to do this:
Through your User Control Panel: User CP, Settings & Options, Edit Ignore List. Then, type their name into the empty text box and click 'Okay'.