A Microsoft PowerPoint XML Open file is a creation of MS PowerPoint - a program that uses a slideshow form to display content. The new extension is based on the previous one, .ppt. Currently, PPTX is the default format for MS Office 2007 and later versions.
The new file contains a number of slides, including text, animations, images, and other media. It is a very useful tool for academic classes as well as business meetings.
Unlike the first version, the new one uses Open XML format. A compressed ZIP package stores the documents as separate files. Resulting in reduced document sizes which makes the files more convenient to use. Due to the fact that the documents are XML-based, they become more adaptable and flexible.
MS Office developed the updated extension as a response to the Open Document Format. The new type can be opened in many apps on various platforms. There are several ways to view and edit such documents: get a copy of MS Office 2007 (PowerPoint 2007) or later, download an app like LibreOffice or edit the file online using Google Slides.
It is still possible to use the first extension if necessary. However, it is better to convert it to the second version to avoid issues with compatibility.