If you had a total City that has a different number than the number in Box 19 on the other page/W-2, you may be missing a page of your W-2's. It's supposed to be City A + City B = Total City. So if your Total City is a larger number than City A and that's all you have then chances are you're missing the part of your W-2 showing City B. You may wish to contact your employer and ask them about it.
With little information to go on, my best guess is that the SD-100 is your Ohio School District Tax form. I'm not 100% on this as there could be other SD-100 forms out there.
