I love this program! It is software for writers, for anyone who has ever tried to pull together a series of words into some degree of coherency. The approach is quite different to the options provided by Microsoft Word or similar styles of programs.
Essentially, the program allows you, the writer, to break your thoughts down to any sized chunk you need (from one word to nigh on infinity, if that floats your boat) and then move them, with ease. Think of digital index cards merged with flexible outlining and freeform collections and searches.
But, you have to try it to understand what I mean (and you can download trial versions).
For too long, it was only available for Mac, but now the Windows version is available, finally out of beta. The Windows version is only 1.0, the Mac option is up to 2.1 (and is even more useful), but the 1.0 option is a far better choice than 0.0.
The company that makes both versions is called Literature and Latte. Follow the link to visit the site, there are plenty of resources there to help you make an informed decision about whether or not the software is for you. And if you do decide to download, I strongly recommend going through the tutorials (on either version) to allow you to get as much as possible out of the software.
I wouldn't normally recommend spending too much time on any user forums these days (the noise ratio is too high on most), but the forum there is of a very high standard and you can find answers to most questions you might have.