CSS custom fonts allow developers to choose from a wide range of custom fonts that align with the brand identity, improving branding and readability. They provide more control over fonts while maintaining privacy, security, and performance. The CSS @font-face rule is used to load custom fonts from a remote server, allowing for greater flexibility and customization. Using font-display property can improve the user experience by loading fonts quickly and providing a smooth visual transition. By understanding how to use CSS custom fonts effectively, developers can elevate the design of their website and provide a better user experience.