I’ve never heard the term “rule set” before. But CSS 2.1 used “rule set” and “rule” interchangeably:
A rule set (also called “rule”) consists of a selector followed by a declaration block.
A selector + declaration block is one type of CSS rule. Specifically, it is a “CSS Style Rule”. That’s to distinguish it from the other types of CSS rules, namely the
@ rules. Both
@ rules and style rules implement the
CSSRule interface in the DOM (technically, CSSOM).
Does it really make a difference to your day-to-day coding? Not unless you’re using the CSSOM interfaces. But I think the main point of Chris’ post is that it helps to have a consistent terminology when you’re talking about a programming language. The words may be made-up and arbitrary, but it helps to know what they mean.
... read the whole story at css-tricks.com.