Excel files are usually .xls
In Office 2007 Excel files that are single pages are still .xls while workbooks (more than one page) are .xlsx
There are other extension for documents that are web pages in Excel, documents that have macros enabled and other such things. To find out, go to your Excel program and click "save as"
When the menu comes up, click on the pull down menu "save as type"
You will be able to see all the different options there.
For a standard Excel document, prior to Excel 2007, it is xls and xlsx is used in 2007. There are other kinds of files created by Excel, like templates which can be xlt or macros which can be xlm and xla for Add-ins, and there are other extenions. For 2007, you add x to the end of them.
For workbooks in Excel 2003, the extension .xls is used.
Ms excel
XLS is the main extension name used in Excel.
XLS is the common extension for an MS Excel (tm) spreadsheet. Therefore chances are the reference you and/or your computer is referring to is an Excel Spreadsheet. To open this file format you must have either MS (Microsoft) Excel standalone, or MS Office installed on your computer.
XLS is the most common extension for Microsoft Excel spreadsheets. It is an acronym that actually stands for "MS File Extension". There is also XLSX and XLSM.
MS Excel does not have a web extenstion. The file extenstion is .xls or .xlsx. If you convert a worksheet to HTML, then the extensiton will be .htm or .html.
MS excel is a part of MS Office suite. You can create spreadsheet with the help of MS excel.
The standard extension for Excel workbooks is xls for versions up to 2003. Excel 2007 uses xlsx as its extension for workbooks.
The extension for excel is .xls
MS-Excel is a powerful worksheet & you calculate , syncronize many hard calculation, so MS-Excel is called Excel.
In MS Excel, each page is called a worksheet.