The ScriptManager is a component in ASP.NET that manages client-side scripts for web applications. It helps in loading and organizing JavaScript files, ensuring that they are available when needed. This is particularly useful for applications that use AJAX to enhance user experience by allowing asynchronous data updates without refreshing the entire page. By using the ScriptManager, developers can easily register scripts, control their loading order, and manage dependencies. It also supports Web Services and ASP.NET AJAX features, making it easier to create interactive and responsive web applications. Overall, it simplifies script management and improves application performance.