Files with DWG extension represent proprietary binary files used for containing 2D and 3D design data. Like DXF, which are ASCII files, DWG represent the binary file format for CAD (Computer Aided Design) drawings. It contains vector image and metadata for representation of contents of CAD files.
Files with ODS extension stand for OpenDocument Spreadsheet Document format that are editable by user. Data is stored inside ODF file into rows and columns. It is XML-based format and is one of the several subtypes in the Open Document Formats (ODF) family. The format is specified as part of the ODF 1.2 specifications published and maintained by OASIS.
You can also convert DWG into many other file formats. Please see the complete list below.