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.
A PowerPoint Template is a file that can contain commonly used settings to make producing future PowerPoint Presentations and Shows easier. POTX PowerPoint Templates are different than the POT version in that they use the Microsoft Office Open XML format.