In "Class Modifieres" you can customize several properties like visibility.
The "Extends" field specifies which class shall be inherited. Only one class my be entered.
The "Implements" field defines which interfaces are implemented by this class. Multiple interfaces can be seperated with commas.
The "Import List" is a list of all classes that shall be imported. Entries like "java.awt.*" are possible, that means all what usually follows the "import" instruction in java source code. You can find some usefull default values in the context menu.
The "Debug - Level" is - just like the one of the packages - used for debugging - output. For more information, see Preferences: Packages.