Take a look into Help file

But seriously…
There are too many things to write about but I think anyone can agree that
clean TC is nothing compared to TC + plugins.
There are almost 500 plugs available with support for hundreds of file formats (i.e.
GAUP which unpacks resources from over 300 games) and someone can be lost with such amount of them but what makes it great is the way how information provided by them is used.
By default they are divided into 4 types:
- wcx - packer plugins for archives support;
- wdx - content plugins for custom columns and Multi Rename Tool;
- wfx - filesystem plugins for external devices;
- wlx - lister plugins for files preview (F3).
Such features are well known since years but there are more places when plugins can be used, so I will try to point few of them:
WCX (content)They are mostly used for unpacking but few of them exist for handling non-archive formats support: like audio files conversion, images resizing, files encryption or directories listing.
WDX (content)Average knowledge: Find files tool, Multi Rename tool and files colouring feature;
Hidden stuff: files tooltips, information File overwrite dialogue, Custom filters, thumbnails labels, File attributes dialogue;
WFX (content)Their use cases vary: external devices support, system Registry editing, CD/DVD burning or… viewing Miranda IM messages. There are many more features available but each WFX plugin is completely different case to be wrote about. Trying to describe them all is just the waste of the time
WLX (content)Average knowledge: files thumbnails;
Hidden stuff: thumbnails in Files overwrite dialogue;
Obviously: that's not all but I don't really think I should try to copy
http://en.totalcmd.pl/download or
http://www.totalcmd.net/. I would rather leave the place for curious explorers.
BUT one thing I must say: even after few years of using TC, I still find something "new" sometimes.