the difference is with an OEM, if your MOBO dies or what have you you basically have to call microsoft and get them to authorize you to add windows 10 to your "new" pc since you have to replace the MOBO. It's just no as easily transferable from one pc to the next. the one I'm getting you can have it on one pc at a time but if some shyt on mine dies and i have to cop new shyt I can just reinstall it no hassle.not sure what the difference is but I got the OEM version cause it was $20 less