Adds some features to TCF that aren't already present.
Augmented TCF adds various features to the Terraria Community Forums.
That's most of what there is, it augments (adds to) TCF!
This includes various features, such as a menu that will stay at the top of the page, a list of images that will be shown under a "custom" tab in the smilies feature of the forum's editor, collapsing quotes to only be one line tall, ability to use the left and right arrow keys to navigate among pages, and more.
Don't like one of the features? You can toggle it! Every feature present in Augmented TCF is in some way configurable, usually including whether it's enabled or disabled, in the options.