It’s long been considered good etiquette when using other peoples resources, to credit their work and/or link to the place you got the resource from. Almost always people are content with this, because they appreciate the work that went into creating something that they then share so others can use or modify, or learn from.
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.