what kinds of files are spreadsheet files?
xls excel extension is the best known and widespread in the spreadsheets generated by Microsoft Excel application. The files that end with the extension .xls refer to a file which contains all the information (data, formats, graphics, formulas, macros, etc ...) in a spreadsheet, which can only be opened and modified using the Excel application.
Save an Excel worksheet in OpenDocument Spreadsheet format. Important: If you want to keep an Excel version of your file, you need to save the file as an Excel worksheet, for example in the .xlsx file format, and then save it again in the OpenDocument Spreadsheet (.ods) format. Click File > Save As >Computer > Browse.