.DWG(drawing)- a file type used for storing two and three dimensional formats, it is used in such programs as INTELLICAD and AUTOCAD

.DXF(Digital exchange format)-File type used as an exact representation of the data in the AutoCAD native file format, the .dxf file has become less useful since AutoCAD has become more powerful.

.DWF(digital web format)-dwf is a secure file format developed byAutodesk for the efficient distribution and communication of rich design data to anyone who needs to view, review, or print design files.

.DGN(Design) This is the file type for CAD file formats which can be supported by microstation, the dgn format has two versions.

.CSV(comma seperarted values)-A file format which is used to store tabular data

.TXT(text)-A file format that is structured for a series of lines containing characters.

.XML(extensible markup lanugage)- a set of rules in machine readable forms which is encoded into documents

.GML(Geography markup language)-is the XML grammar defined by the open geospatial consortium to express geographical features.

.KML(keyhole markup language)- is an XML schema for expressing geographic annotation and visualization within internet based, two-dimensional maps and three-dimensional earth browsers.

.KMZ(Keyhole markup-zipped) A kmz file is a zipped keyhole markup language used to decrease the size of data.

Info source-http://www.wikipedia.org/