When you add content to a page, some portlets (for example, the Open Manage Network Manager Container View portlet) appear with a purple icon and others (for example, the Authentication or Container Manager portlets) have green icons. The green-icon portlets are instanceable and the purple-icon portlets are non-instanceable.
In other words, you can add only one instance of the (purple-icon) Container View portlet to a community; and it displays the same data, even if it appears on more than one screen.
Once you have added a non-instanceable portlet to a page, its entry in the Add menu appears grayed out and disabled. You can add more than one non-instanceable portlets to different pages, but they display the same data. Instanceable portlets can appear multiple times on the same page, and can display different data.
The Authentication portlet, for one example, is different. You can add it many times to pages in the community, and can configure each instance of the portlet to display different authentication data.