Messenger Plus! is a great program with many great features. But it is impossible to put all great features in one program: many people would only use a fraction of the features available.
Plug-ins can take over a small part of that problem. Plug-ins can add new features to Messenger Plus! that Plus! itself does not have. Examples are extra sounds (Audiator), sending screenshots (Screenshot Sender) or even a lot of other features (StuffPlug NG; search these forums for those plug-ins).
Simply put: by downloading and installing plug-ins, you can add more features to your Messenger Plus!. A list of plug-ins can be found at
http://plugins.msgplus.net - and at
http://shoutbox.menthix.net/forumdisplay.php?fid=28 you can find the plug-ins forum for questions.
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