Firstly, they're pretty much an evolution of Web 2.0 and have become popular among many other types of site. Social networks are full of them and I'm sure most have already used them before.
Here's what you do: Just tag your threads or other people's threads and it basically gives us keywords to sort and find information and other threads. From within a thread that's tagged, IE, "Israel", you can click the thread and find others which have the same tags.
Let me know if you have any questions