XML is a format used to store data that can contain not only text but also binary information or media like images, audio, video. It uses a structured format and nowadays it is widely adopted in many different sectors to exchange data between computers and as a file format that is easily versionable.
Recent versions of PowerPoint supports XML format in its new pptx output format for presentations (actually it is a zip archive that if you rename from pptx to zip you can open it in WinRAR or WinZip and then find a lot of .xml files inside with presentation media and resources). But if you still need to save your presentation to .xml then you can do that in the Save As dialog.
Go to File and then Save As and now you can open the Save as type to choose powerpoint XML Presentation (*.xml). Once accepted, your presentation will be saved to XML.
Viewing the XML File
You can open XML files for editing using a plain text editor or any other XML tool. At a glance you will see a series of complicated tags and code that contain the data regarding your powerpoint presentation but after checking carefully you will notice the data is well structured and it can be easily handled by an application or converter