The OneNote notebook for each CRM record will be automatically created and be available in all CRM apps. To access a notebook, ...

The OneNote notebook for each CRM record will be automatically created and be available in all CRM apps. To access a notebook, a user navigates to the form and chooses the OneNote tab (in the activity wall). Note that section groups in a OneNote notebook aren't supported.
This doesn't replace the current Notes feature, but gives users another way to access notes stored in OneNote.