Think of tags as like a book index where you find words and which pages they are on, the same principle applies here. Although it's taken a stage further so it might not be the word, but the subject, so for example if you're looking for things to do with fractal gradients for example. A tag may bring back posts with gradient files, as well as posts that discuss gradients, or tutorials about them.
“JWildfire is a free and user-friendly image-processing software, mostly known for its sophisticated flame-fractal-generator. It is Java-based, open-source and runs on any major computer-plattform. There is also a special Android-version for mobile devices.”