Question: what is the difference between pst and ost files used in outlook?
Answer: ost-files. The main difference between these two file types is that pst-files are being used for “actual” storage and ost-files are being used for “cached” storage. ... As of Outlook 2013, IMAP accounts are also cached in ost-files. Another exception is that some folders within an ost-file do not sync with the mail server.