A portlet mode indicates the function a portlet is performing in the render method. Normally, portlets perform different tasks and create different content depending on the function they are currently performing. A portlet mode advises the portlet what task it should perform and what content it should generate. When invoking a portlet, the portlet container provides the current portlet mode to the portlet. Portlets can programmatically change their portlet mode when processing an action request.
The Portlet Specification defines three portlet modes, VIEW, EDIT, and HELP. The PortletMode class defines constants for these portlet modes. Every portlet must support VIEW mode and optionally it can support EDIT and HELP mode