Files with DWG extension represent proprietary binary files used for containing 2D and 3D design data. Like DXF, which are ASCII files, DWG represents the binary file format for CAD (Computer Aided Design) drawings. It contains a vector image and metadata for the representation of the contents of CAD files.
Files with CSV (Comma Separated Values) extension represent plain text files that contain records of data with comma separated values. Each line in a CSV file is a new record from the set of records contained in the file. Such files are generated when data transfer is intended from one storage system to another. Since all applications can recognize records separated by comma, import of such data files to database is done very conveniently.
You can also convert DWG into many other file formats. Please see the complete list below.