WMF stands for Windows Metafile; EMF stands for Enhanced Metafile. These files drive Windows to display an image. Within Microsoft Office applications it is a standard format for vector images.
The Metafile is managed by Microsoft and is not an open format. The format does not receive good support outside of large applications. The format is based on Windows and the specification is not stable.
Software such as Inkscape or Adobe Illustrator can convert WMF and EMF files to the preferred SVG format.
WMF is a non-preferred format for file type Images (vector).