What is the difference between Excel XLSX and XLSM?

Answer 1

File stored in XLSX format are standard Excel files. Files stored in XLSM format can contain Macros and VBA (Visual Basic for Applications) code, the programming language to automate tasks in Excel. Macros and VBA code can potentially be very dangerous as the VBA language has access to the inner workings of your computer. VBA code can be programmed to, among other things, reformat disk drives, delete files, and surreptitiously send files to another computer using email.