A POTM file is a macro-enabled presentation template created by Microsoft PowerPoint, a program used for creating slide show presentations. It contains default images, slide templates, macros, and formatting. POTM files are used to create multiple .PPTM files with the same formatting and macro settings.
HTML is a Web format file. HTML source code can be changed in a text editor. HTML files are being developed for future use in the users web browser, allowing you to format text, images and other materials required sites. File with this format use tags to build web pages. HTML code is parsed Web browser and usually not visible to the user.