An application extension unlike an asset extension only allows a developer to either develop new endpoints (pages or APIs) or override existing endpoints. This is useful whenever a common page that is accessible by all asset types needs to be developed. As an example, the ES Store application provides a top assets view that displays the top assets for each of the asset types.
An application may have one or more extensions as shown in the diagram above. However, it is advised to group all customizations into a single extension to improve maintainability. The next diagram presents a closer look at an extension.