what are the default portlets we see in Dockbar - Add menu?

The first icon that you will see in the Dockbar is a pin-like icon and The second option you will see in the Dockbar is Add.

In the "Add" the options are divided into two broad areas—Page and Applications

Page: When you  click on Page, it will add a new page to the same level as you are. You can also see the newly added page in the page navigation.

The second area is Applications, which is a portlet in the portal world. By default, it displays
four commonly-used portlets—

Web Content Display,
Asset Publisher,
Document Library Display, and
Navigation portlets.


You can also change the list of the default portlets by modifying the dockbar.add.portlets property in the portalext. properties file. You need to specify the portlet ID in a comma-separated list.