XLSX is the default file format in Excel 2007 and later, and is used for regular spreadsheets that do not contain macros or other advanced features. XLSM is a file format that supports macros and is similar to XLSX, but has a different file extension to indicate that macros are included. XLSB is a binary file format that is optimized for performance and can handle larger spreadsheets more efficiently than XLSX or XLSM.