What is a CSS Selector?

CSS selectors are used to "find" (or select) HTML elements

The three most common CSS selectors are the id Selector, class Selector, and element Selector.

id Selector

The following CSS selector will select all elements with an id "first-name"

#first-name

class Selector

The following CSS selector will select all elements with a class "credit-card-form"

.credit-card-form

element Selector

The following CSS selector will select all paragraph <p> elements

p

You can combine selectors as well

div.credit-card-form

Read more about CSS selectors on the web.