The OST and PST files are data file types used by Microsoft Outlook to store information, but they serve different purposes and are used in different situations. 1. OST (Offline Storage Table) Purpose: OST files store a synchronized copy of your Outlook mailbox on your computer. They are mainly used for offline access to emails, calendar events, and contacts when you don’t have an internet connection. 2. PST (Personal Storage Table) Purpose: PST files store Outlook data locally and can hold emails, calendar events, contacts, tasks, and more. PST files are mainly used for personal backups or when you are working with a POP3 account. Check for more details at: https://www.zooksoftware.com/ost-to-pst/