A metafile is a file that contains specifications for another file. Metafiles are commonly associated with digital graphics, particularly vector images. However metafiles can contain other formats as well, such as bitmaps or other data. Metafiles that contain audio, video and (in some cases) text are often referred to as container files.
The word "metafile" basically translates to "beyond" or "before" file. With that, the metafile is meant to serve some outside function to an existing file. Use of the word "file" to explain electronically stored data can be traced back to an RCA advertisement for electron tubes in 1950. Since then, files have broadly expanded in format, function and capability. The metafile is typically used to outline specifications for a graphic image file, but metafiles have also evolved to perform other functions over the years.