.xltx
Excel template
A starting point for new Excel workbooks. Opening it creates a fresh, untitled copy, so the layout, styles and formulas in the template itself stay unchanged.
Reusable layouts such as invoices, budgets and timesheets that you fill in again and again.
Opens in Excel, LibreOffice Calc
About XLTX files.ods
OpenDocument spreadsheetOpenDocument Spreadsheet
The spreadsheet format of the OpenDocument standard (ISO/IEC 26300) and the default in LibreOffice Calc. A zipped set of XML files holds sheets, formulas, styles and charts.
Spreadsheets kept in an open, vendor-neutral format, common in LibreOffice and the public sector.
Opens in LibreOffice Calc, Excel, Google Sheets, Collabora Online
About ODS files