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.
Files with ODP extension represents the presentation file format used by OpenOffice.org in the OASIS OpenDocument standard. A presentation file is a collection of slides where each slide can comprise text, images, formatting, animations, and other media. These slides are presented to an audience in the form of slideshows with custom presentation settings.
You can also convert PST into many other file formats. Please see the complete list below.