Following are the important Excel file formats you should remember, while working in Excel.
• XLSX file format : XLSX file format is and XML based file format which is the default Excel file format since Excel 2007. You cannot store VBA macro code inside an XLSX file. Click below link to know more about Excel XLSX file.
• XLSM file format : XLSM file format is also XML based file format, but you can store VBA macros inside XLSM files. Click below link to know more about Excel XLSM file.
• XLSB file format : XLSB file format is binary file format, not XML based. Since XLSB file format is binary file format, it allows fast loading and saving. XLSB file format is very useful for very large Excel spreadsheets. You can store macros inside XSLB files.
• XLTX file format : XLTX file format is used for creating Excel Templates. Templates are predesigned Excel files, which you can use as the base to create your own spreadsheets. Using templates as the base to create your own spreadsheets can save your precious time. You may use the functions are other features which are already in Excel template. XLTX file format does not support VBA macros.
• XLTM file format : XLTX file format is also used for creating Excel Templates. The main difference between XLTX file format and XLTM file format is that in XLTM files, you can store VBA macros.
• Excel 97-2003 XLS file format : Excel 97-2003 XLS file format was the legacy native file format for Excel 97 to Excel 2003 versions.
• Excel 5.0/95 XLS file format : Excel 5.0/95 XLS file format was the legacy native file format for Excel 5.0 to Excel 95 versions.
• XLAM file format : XLAM file format is used to define Excel Add-Ins. Excel Add-Ins are used to add extra functionality to Excel by writing new functions using VBA code.
• XLM file format : XLM file format is used to create Excel 97-2003 Add-In.
Click below linkt to learn Difference between xls, xlsx and xlsm file formats