Each note belongs to its own group.
When program starts for the first time there is only one group - "General". Every new note is created in this group by default.
You may add, modify or remove groups at PNotes.NET Control Panel. Each group may have its own settings, including icon, background and caption font color (for skinless notes), skin (for skinnable notes) and font.
Any note created in specific group or transferred to it inherits group settings. You may change note's group either by simple drag-n-drop on PNotes.NET Control Panel or by using note's "Rename/Change Group" menu and choosing desired group.
If any group is selected on PNotes.NET Control Panel, then new note will be created in this group, although you may always change the group when you save note.