A selector represents a structure. This representation is then used in a CSS rule to determine what elements are selected to be styled by this rule. CSS style rules apply in the form of a waterfall effect. Each rule that is matched is also passed on to each of its children, matched and applied based on the weight of the selector. This section will only focus on the most basic of selectors.
The basic selectors are either type selectors, universal selectors, attribute selectors, class selectors, ID selectors, or pseudo-classes.
Note
All CSS selectors are case-insensitive. Selectors can also be grouped together to share rules. To group selectors, you just have to split them with commas. Consider the following example:
p { color: #ffffff; }
article { color: #ffffff }Here, the following is the same as the preceding declaration
p, article { color: #ffffff }