Checkmarking "Start components as needed" configures an application or application server to only start components as they are needed.
This option is not checked (disabled) by default, so that all components are started. Enabling this option can reduce the time it takes the application server to start up. Enabling this option typically makes sense when all of the application in the application server are similar use similar resources, such as a JDBC connector. You can either configure the entire application server to parallel start or you can configure a single application to parallel start.
Start components as needed - Application Server
Start components as needed - Individual application