Over the years Excel has used several different file extensions to denote that the file is, indeed, native to Excel:
- XLS. An Excel 97 through Excel 2003 workbook file.
- XLSX. An Excel 2007 (or later) workbook file.
- XLSM. An Excel 2007 (or later) workbook file that contains (or can contain) macros.
If you use the Open dialog box to open any type of file besides these three, Excel will dutifully attempt to translate the information in that file into a meaningful format. For instance, if you attempt to open a file that contains nothing but text, Excel will read the information and place it in an otherwise blank workbook.
Excel can read files created by several other types of programs. The types of files you can open depend on your version of Excel. If there is any confusion as to how Excel should translate the file, it will ask you to select the type of translation to use.
When you load a file created by another program into Excel, you should understand that you might lose some formatting that is unique to that particular program. Rest assured, however, that Excel will do its absolute best to faithfully translate and load the file as you requested.