Portlet has different modes for performing personalization, customization and configuration for different users and for different portlet instances.
Here is a quick introduction of different portlet modes Personalize, Edit_Defaults, Configure and their acess rights.
Personalize: Updates change the look of the portlet only for the user who makes the updates. In order for a user to have access to personalize settings, they must be granted at least Privileged User role on the page and Privileged User role on the corresponding Portlet Definition. This is available for standard portlets and IBM portlets.
Edit Shared Settings: Updates change the default look of the portlet on a specific page. All users see the change when they access that page. In other words, all (the particular) portlet instances on a page are modified, but not all instances of that portlet on every page. If you want the changes to appear on every page that portlet appears, you must modify the settings on each page. In order for a user to have access to edit shared settings they must be granted at least Editor role on the page and Editor role on the corresponding Portlet definition. This is available for standard portlets and IBM portlets.
Configure: Updates change the default look of a portlet for all portlet instances. All users see the portlet changes on all pages that portlet is available. A user needs to have at least Manager role on portlet definition to have access to configure a portlet.
For more better understanding, have a look at this