What are the differences between classes and IDs in CSS?

• Uniqueness: ID is unique on the page, while a class can be applied to multiple elements.
• Specificity Priority: ID has a higher specificity priority (100) compared to class (10).
• Selectors: ID selector is denoted by #, class selector by ..
• Usage: ID is usually used for styling individual, unique elements (e.g., header, footer), classes for styling groups of elements with common properties (e.g., buttons of different colors).

/* Styling by ID - applied only to one element */
#header {
  background-color: blue;
}

/* Styling by class - applied to multiple elements */
.button-primary {
  color: white;
  background-color: green;
}

Attribute	Class	ID
Uniqueness	Not unique	Unique
Priority	10	100
Syntax	.class-name	#id-name
Application	Groups of elements	Unique elements