Files with the extension POT contain a template, ie a template for a Microsoft PowerPoint presentation. These files contain various formatting information, such as fonts and sizes, images and colors, and texts can also be included. They can be used to create multiple presentations with the ending ppt, all using the same style.
Microsoft supplies some templates with PowerPoint, but many templates are also available for free or available for purchase.
The POT files are used by versions 97 to 2003 of Microsoft Powerpoint. The newer versions as of 2007 use the extension potx for their template files.