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.
Texture Gpattern & Gosper Island image set to be used for mapping in J … Details
The blob variation pushes and pulls the plane to make it look like a blob. Specifically, it takes a sine wave, wraps it into a circle, and uses that to distort the plane. The pictures below show respectively a sine wave, a radial sine wave (one wrapped into a circle), and a circular dc_perlin texture before and after applying blob.