Pst-files, when you are using a POP3 account, Outlook can’t live without them. Outlook 2010 and previous also used pst-files for caching IMAP data.
Pst-files can also be used for additional storage, archives and exports, even when you are using an Exchange or Outlook.com/Hotmail account.
In other words; Pst-files are pretty important to Outlook and knowing how to properly treat pst-files is one of the more important basic Outlook skills as well.
This guide contains these basics but also more advanced and additional background information about the pst-file and how you can handle them.
Continue reading: About the Outlook PST-File