Macro-enabled spreadsheet created by Microsoft Excel, a spreadsheet program; contains worksheets of cells arranged by rows and columns as well as embedded macros programmed in the Visual Basic for Applications (VBA) language; saved in the Open XML format introduced in Microsoft Office 2007.
XLSM files are .XLSX files, but with macros enabled. They may be opened with Excel 2007 or later, or by previous versions of Excel with Open XML component support. For security reasons, Excel does not enable macros by default.
NOTE: Excel will not execute macros in XLSX files, even if they contain macro code. They must first be saved as XLSM files.