Could you please be more specific ?
Foundation objects are used to define organization, pay and job structure such as Company, Business Unit, Division, Department etc. Some of the FOs have been migrated to MDF and hence called as MDF FOs. FOs are designed keeping in mind the organizations structure whereas Person objects refer to the employees in particular.
Genreic objects basically points to the objects defined using Configure object definitions. For e.g. Time off related objects, Position object etc.
Employment objects : As the name suggests it specifies employment details such as hire date, termination date, global assignment information and compensation information as well.
Have a nice day!