Files ending in PPTMHTML are MIME HTML files created by earlier versions of the Microsoft PowerPoint presentation software. Among other things, these files contain HTML source code similar to an html file. The source code is created in such a way that the browser displays a ppt document as similar as Powerpoint. Pptmhtml files can also contain other resources like pictures.
The PPTMHTML 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 Excel save HTML code as an html file.