Personal Storage Table (PST/Outlook Data File), Personal Folder File (PFF)
PST File or Outlook Data File is the file storage facility developed by Microsoft Co. in order to keep entire Outlook data including Emails, Attachments, Contacts, Notes, Calendars items, Task, etc. PST File is constructed using Binary data file algorithm and at the logical level, it is divides into three different layers: NDB (Node Database), LTP & Messaging Layer.
This file format belongs to Database File category.
As stated above, Microsoft Co. is the creator of MS Outlook and all the pertained stuffs. As from 1997, the Outlook term has coined in the Tech world and since then there have been lots of upgrade seen in this email client in past decade.
ANSI (97–2002 Personal Folder File)
Default file format for older versions of Outlook (97–2002) capable to hold data up to 2 GB, does not support multiple languages, structure is a 32–bit unsigned value. However, Outlook still provides an option to create ANSI PST file even in its latest versions of Outlook whilst creating a PST File.
UNICODE (2003 – 2016)
UNICODE (2003 - 2016) is multi-lingual data file format, 64-bit unsigned long, can handle data up to 50GB (massive amount of storage capacity), and cannot run in older version of Outlook (count as a drawback).
MS Outlook 2016
Outlook 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\
MS Outlook 2013
Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\
MS Outlook 2010
Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\
MS Outlook 2007
Outlook 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\
MS Outlook 2003
Outlook 2003: HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\
Note: You can also find out the location of PST file using "Account Settings" option available in Microsoft Outlook's settings.