Its a Wiki type thingy, which means collaboration to me, but its implemented 100% on the client side, which, yep you guessed it, means there's no server side logic managing things like identity, repository access, concurrency, versioning, etc.
TiddlyWiki in its entirety is one single HTML file. It doesn't support persistence of changes and its not even editable "out of the box".
Sound weird? It is. But you haven't heard about the "Tiddlers" yet.
To quote the creator, "TiddlyWiki is fundamentally different from a conventional Wiki because it is not based on separate, entire pages of content, but rather items of micro content referred to as Tiddlers that live together on the same page."
The other unique concept is TiddlyWiki's navigation paradigm. I guess we can say that its very "Ajaxy", though technically that is not at all correct. Its certainly Web 2.0, as if that meant anything.
In short, when you start clicking internal TiddlyWiki links, instead of page refreshes, you get these Tiddly things appearing with a standard Tiddly toolbar that lets you control its visibility and investigate and jump to its relationships with other Tiddlies in your TiddlyWiki thingy.
The whole experience is a bit like an intergalactic Scriptaculous demo
, but progressively the thing does start to make some sense and one must admit that the idea of a self-contained micro-content web on stick kinda sounds sexy. And if you can figure out what to do with it, it might even get you promoted or at least confuse the right people at the right time.