1/ Selectors combined in a comma-separated list so you can apply the same properties to them all.

Grouped property

Grouped style

Grouped value

Grouped selector

2/ The concept that some selectors have more weight and therefore override rules with less specific selectors.

Specificity

Cascade

Rule order

Box model

3/ Selects all the elements in a document of a given element type.

Style selector

Property selector

Element type selector

Grouped selector

4/ Provides a list of elements to be selected, separated by commas.

Grouped selector

Element type selector

Property selector

Style selector