A PST (Public Storage) file (.pst) is a Personal Folder file in Microsoft Outlook and can be stored on a user’s local hard drive, or cloud drive.
An OST (Offline Storage) file (.ost) is an offline folder file in Microsoft Outlook and is used to sync with the Exchange Server (where the emails live). [Note: If user isn’t on an Exchange Server the OST file might be stored on user’s local hard drive, or cloud drive.] The OST file allows users to continue to work even when they don’t have access to the server. It stores any changes made in Outlook while in offline mode (not connected to the server), and once the user re-connects to the server it will sync with the server, pushing any changes that were made while in offline mode.
