What is Specificity?
Each CSS selector has a specificity value, and more specific selector has the higher precedence it has. If multiple selectors apply to a single element, the highest specificity CSS rule apply to the element. Have you had an experience where you define a CSS rule for an element, and it doesn't work? You probably have a CSS rule that has a higher specificity value which causes your newly created CSS rule to not apply.
Which CSS rule applies to an element?