Microsoft Outlook creates a PST file, while you configure an
account in Outlook. The PST stores copies of messages, calendar,
notes, tasks, contacts and other items.
PST file may get corrupted because of many reasons, in that
case, you would be unable to open Outlook. The reasons could be
Virus, improper outlook shutdowns, corruption in header files, pst
file has reached maximum size limit etc.
In that case you can use outlook utility, named Inbox repair
tool to fix your pst file.