What are selectors in CSS?

When you are writing CSS (Cascading Style Sheet) code, you are writing a set of rules that a page's HTML code must follow when rendering the page.

Every block of CSS rules has three important parts: The selector, properties, and values. The selector is what tells the page WHAT elements the following rules apply to, such as all divs with a name of "colorMeRed". Properties are what the page must change on the element, such as it's color. Finally, the value is what that property actually must be set to, such as "red".