365 may be installed on up to 5 machines on the purchased licence. This is owned by what I shall call the Owner account. Each licence grants 1tb of Onedrive cloud space.
A Windows user on any machine may, but need not, be logged into an Office account. Possibles are:
Log into the Owner Account. This is the most common. This gives access to the 1tb Onedrive space bundled with Office 365. Office programs (Word, Excel etc) can access files on the local network and also files stored on the Owner account Onedrive cloud.
Log into a Different (Office) account. This gives access to files on the local network and also files stored on the Different account Onedrive cloud. It does not grant access to Onedrive files belonging to the Owner account.
Don’t log in at all. This just gives access to files on the local network.
With (1) and (2) there is sometimes confusion. Word/Excel may save direct to the Onedrive Cloud instead of locally without giving any indication. This can be prevented by ticking the “Always save to disk” under Option:Save
Onedrive can be set up to syncronise with a folder on a local disk. The folder location can be customised but it is always in a folder called “Outlook” or “Outlook company abc”. This is annoying as it means that one cannot specify the actual folder name (as one can in Google Drive Sync).
Multiple OneDrive syncs can be set up on the same computer even for . The number of computers syncing to any Onedrive does not appear to be limited.
Individual OneDrive folders may be shared online but syncronisation is all-or-nothing unless a 3rd party product like EgNyte is used.