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 ICO extension are image file types used as icon for representation of an application on Microsoft Windows. These come in different size, colour support and resolution to suit the requirements of the display. Another similar image file format on Microsoft Windows is .CUR for cursor representation and defines a hotspot in the image header. On MacOS, ICNS file formats serve the same purpose as ICO files. Several online websites as well as applications provide the feature of creating such files and convert other image formats such as BMP, PNG, etc. to icon file format. The official IANA registered Internet media type for ICO files is image/vnd.microsoft.icon.
You can also convert DWG into many other file formats. Please see the complete list below.