CSS properties are the building blocks of styling web pages. They define how HTML elements should be displayed on the screen. Each property has a specific function, such as changing colors, fonts, spacing, and layout. For example, the color property sets the text color, while the margin property controls the space around elements. There are hundreds of CSS properties available, each with its own set of values. Properties can be combined to create complex styles. Understanding these properties is essential for web developers and designers to create visually appealing and user-friendly websites.