Almost the same as inbox but here you can see only the notes you have not read yet
In the starred section are stored all notes that you have starred. You can use this to mark important notes.
Sent notes section is a section where your sent notes are stored until they are deleted.
You can save your notes as a drafts and they will be stored in this section so you can use them later if you want to.
You can mark sender as a spammer and all notes from him later will go in this section and will stay there.