There is only one file type that uses the .VML extension:
Vector Markup Language File
File created in the XML-based Vector Markup Language (VML) format; contains XML code that describes a vector image; commonly embedded within published HTML pages to display vector images.
While the VML standard is no longer being developed, it is still supported by various Microsoft software products. In particular, Microsoft Internet Explorer supports VML image rendering in Web pages. VML is also used by Google Maps within Internet Explorer.
Updated: September 9, 2014