Quick Notes are the electronic equivalent of little yellow notes. When you create a Quick Note, it's saved immediately as a section in <your name> Notebook. OneNote uses both the Quick Notes and <your name> Notebook to sync your notes to OneDrive. For this reason, don't rename the <your name> Notebook or the Quick Notes section.
Tip: Quick Notes are being replaced by Sticky Notes for Android phone. Sticky Notes are the best way to quicky capture notes and view and edit them across your favorite devices. Learn how to Add content to your sticky notes.