Files ending in PPTHTML are HTML files created by earlier versions of Microsoft PowerPoint. PowerPoint, the standard presentation software from Microsoft Corporation, usually stores presentations (slideshow) as a ppt file. To view his documents in a browser, the user can save his document as a PPTHTML file.
This file then contains normal HTML source code similar to an html file. The source code is created in such a way that the browser displays the document as much as PowerPoint does.
The PPTHTML format is no longer supported by Microsoft. Documents that should be published on the Web should therefore be saved as an mhtml or mht file.
Newer versions of Microsoft Word save HTML code as an html file.