Windows stores graphical objects (i.e., pictures) in a special form called a metafile. Such pictures can be stored on disk or in the Windows Clipboard. When these pictures are imported (or pasted from the Clipboard), the objects can be optionally separated and stored individually.
Windows Metafiles are intended to be portable between applications and may contain both vector and image components. In contrast to raster formats such as .JPEG and .GIF which are used to store image (bitmap) graphics such as photographs, scans and graphics, Windows Metafiles generally are used to store line-art, illustrations and content created in drawing or presentation applications. Most Windows clipart is in the .WMF or .EMF format.
Windows Metafile .WMF is a 16-bit format introduced in Windows 3.0. It is the native vector format for Microsoft Office applications such as Word, PowerPoint, and Publisher. A newer 32-bit version with additional commands is called Enhanced Metafile (EMF). EMF is also used as a graphics language for printer drivers.