Feeder Class 
A feeder class provides a link between the application and the generic user interface building block (GUIBB).
Feeder class implementations are based on a predefined interface definition, providing all necessary methods and corresponding signatures to standardize the communication between the application and the GUIBB.
A feeder class is a class that implements one of the following ABAP interfaces:
IF_FPM_GUIBB_FORM (for form components)
IF_FPM_GUIBB_FORM_REPEATER (for form repeater components)
IF_FPM_GUIBB_LIST (for list components)
IF_FPM_GUIBB_SEARCH (for search components)
IF_FPM_GUIBB_TREE (for hierarchical list components)
IF_FPM_GUIBB_LAUNCHPAD (for launchpad components)
Using the GET_DEFINITION method, the class defines the field catalog (the fields that are available for use in the configuration) of the component and supplies the component at runtime with data from the application using the GET_DATA method.
Integration
Feeder class settings can be accessed in the Floorplan Manager configuration editor, FLUID; see the General Settings panel of the individual GUIBB component.