Wagn is not just a wiki, it's also a database.
A database is a structured set of information. People use databases like Wagn for recording all kind of things: organizational membership, accounting data, music collections, etc.
Wagn's approach to data structure is very organic. Often we start gathering information without any structure at all, just using Wagn like a normal wiki. Then, as we recognize patterns, we start creating types. For example, if you were using Wagn to keep an online library of all the books in your house, you might create a card type called "Book".
You might decide that you want to collect certain kinds of information about each book. Things like author, publisher, personal reviews, favorite excerpts, and so on. Wagn can help you organize both your data and its presentation. Just as each book is a card, so is each bit of information about it (author, publisher, etc.). Wagn's approach is to make the book card include all the other cards, which we accomplish by creating a format card for books.
If you want to see Books organized by author or publisher, you can find specific groups of cards dynamically on Wagn using its innovative query language. Wagn makes it possible to query by many things that emerge naturally as you organize information: links, nesting, names, content, types, who edited, when, etc.
One of the most exciting things about using Wagn as a database is that, unlike most databases, the public-facing website and the database are all wrapped up into one. With conventional tools you have your data structure (aka model), where you store everything, your web interface design (aka view), and a whole layer of programming to communicate between the two (aka controller). Then, if you want to change any one of them, you often have to change all three! Wagn wraps all of these into one simple organizing unit: the card.
Look at this page. It's a lot less scary than your average database interface, right? Most database interfaces look much more intimidating, but Wagn just looks like ... a webpage. That's why Wagn can simultaneously be a wiki, a database, and a content management system.