We can choose which permissions are associated with these permission levels (except for the Limited Access and Full Control permission levels) or add new permission levels to combine different sets of permissions. We can associate permissions with permission levels and also associate permission levels with users and SharePoint groups. Users and SharePoint groups are associated with securable objects such as sites, lists, list items, libraries, folders within lists and libraries, and documents.
-: How to Copy an existing permission level:-
§ On the Site Settings page,
§ Under Users and Permissions,
§ Click Site permissions.
§ In the Manage section of the ribbon,
§ Click Permission Levels.
§ In the list of permission levels,
§ Click the name of the permission level you want to copy.
§ At the bottom of the page,
§ Click Copy Permission Level.
§ On the Copy Permission Level page, in the Name field, type a name for the new permission level.
§ In the Description field, type a description for the new permission level.
§ In the list of permissions, select or clear the check boxes to add permissions to or remove permissions from the permission level.
§ Click Create.
If you have any queries/questions regarding the above mentioned information then please let me know. I would be more than happy to help you as well as resolves your issues J J