What are .pst & .ost?

[FARAZ QURESHI]

What are .pst & .ost and and the main differences between them?
Are both the same sort of nature?
Can I have both sort of files/folders on Outlook 2003 or 2007?

 

[Roady [MVP]]

pst-files are files that contain "originals" and in general associated with
POP3 mailboxes.
ost-files are files that contain an off-line copy of a mailbox and are
unique to that mailbox and in general associated with Exchange mailboxes.

Also see http://www.howto-outlook.com/faq/aboutpst.htm