Site speed refers to how quickly a web page loads and becomes interactive for users. It is measured in seconds and can significantly impact user experience. Faster loading times lead to higher user satisfaction, while slow sites can frustrate visitors and increase bounce rates. Improving site speed involves optimizing various elements, such as images, scripts, and server response times. Tools like Google PageSpeed Insights can help website owners identify areas for improvement. A faster site not only enhances user experience but can also positively affect search engine rankings, making it an essential aspect of web development.