Graphics Meta Files Research

http://graphicssoft.about.com/library/glossary/bldefmetafile.htm - this information is from a link and it basically told me what meta files is and what types of files it can go in.

Definition: Metafiles are graphics that contain both raster and vector data. For example, a vector image that contains an object which has a bitmap pattern applied as a fill, would be a metafile. The object is still a vector, but the fill attribute consists of bitmap data. Common metafle formats include WMF (Windows Metafile), EMF (Enhanced Metafile), and CGM (Computer Graphics Metafile).

http://whatis.techtarget.com/definition/metafile - This is were I got the information below from, I thought it was really relevent information because it explains what meta files are and what they do. And why they are useful.
 

A metafile is a file containing information that describes or specifies another file.

Microsoft uses this term for its Windows Metafile (WMF) format. A WMF file contains a sequence of graphical-device-interface (GDI) function calls ("commands" to the Windows operating system ) that results in the presentation of a graphic image. Some of the function calls are equivalent to vector graphics statements and others identify stored bitmap or literal specifications of which bits to illuminate ( raster graphics images). Using WMF files rather than already-built bitmaps saves space when many bitmaps are used repeatedly by different components of the operating system or of an application. The WMF file assumes a 16-bit operating system. Microsoft has an enhanced metafile (EMF) format for its 32-bit operating systems. Microsoft's clipboard (CLP) file can contain a WMF file, an EMF file, or a bitmap (BMP) format file.
Another example of a metafile is the Computer Graphics Metafile (CGM). The CGM file format is a standard ( American National Standards Institute -approved) format that can be used on any operating system that supports it (unlike the WMF format which is designed only for Windows). The CGM file is commonly used in CAD and presentation graphics applications.
In general, there are tools (such as HiJaak) that will convert the WMF, EMF, and CGM formats into other formats.