Files with .PST extension represent Outlook Personal Storage Files (also called Personal Storage Table) that store variety of user information. User information is stored in folders of different types that include emails, calendar items, notes, contacts, and several other file formats. PST files are used for archiving emailing data offline that can be later loaded and viewed in various applications.
Enhanced metafile format (EMF) stores graphical images device-independently. Metafiles of EMF comprises of variable-length records in chronological order that can render the stored image after parsing on any output device. These variable-length records can be definitions of enclosed objects, commands for drawing, and graphics properties critical to render the image accurately.
You can also convert PST into many other file formats. Please see the complete list below.