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.

gaussian blur3

Blur Flame Pack

Blur Flame Samples to go along with the Blur Variation Information page by  Rick Sidwell … Details

blob variation information 1

Blob Flame Pack

Selection of example blobs to go with Rick Sidwell’s tutorial