ServletContxt is the largest of the four scopes of the Web. Its scope is the entire web project. ServletContext is a global storage space for information. When the server starts, it exists, and when the server is shut down, it is released.
ServletContext generally stores important shared information for the entire web project.
The servletContext is the context of the container servlet, which is useful during the entire Tomcat startup process.
Application is a built-in object in jsp, equivalent to servletContext.