What can TiddlyWiki not be used for? That's why it is a hard thing to explain.
Lately, I've been describing TiddlyWiki as this:
Picture Wikipedia, but a personal version just for you. And it is all in one file. You just need a web browser to use it (type of device doesn't matter, don't need any other software), and you can keep that file wherever suits you best. If you store it locally (hard drive, USB thumbdrive, SD card...), you don't need the web to use it. It works in your browser offline as well as online.
Now take out all of the content in Wikipedia so that you have just the stuff that makes Wikipedia work (enter content, edit content) so that you have a clean slate, a blank canvas.
Now you can do with it whatever you want.
- A replacement for post-it notes? (Or notepad on steroids.)
- An inventory of CD's or whatever?
- A Personal Information Manager (aka PIM)
- Organise your notes for a class or keep track of a bunch of things for a project?
- A "Getting Things Done" solution?
- You want to use it as a way to write the different parts of a novel and easily move the parts around?
As-is, you can do a whole bunch of things with it.
But you can use it to build anything. Think: dBase/Access-type stuff. You can build forms to put data/content in it, but you can create queries (with widgets and filters) to get stuff out if it listed in unlimited ways, just like a database.
Overtime and at your speed, you can build it up into a full-fledged personal database application.
I'm a software developer and systems analyst, so TiddlyWiki for me is a platform for application building, either just as prototypes or as full-fledged end-products.
TiddlyWiki is small, but it is the mightiest thing around for everything from the simplest tasks to some seriously complex ones.
The community of users have come up with some wickedly good stuff. I'll share some of mine (which are all at various stages of quality):