keyboard isnt working

I got this mac in november and have loved it! Out of the blue today, I notice when I type z / y they are opposite! for example, when I use the z, I type the y...if you can follow that. Alot of the symbols are also messed up. Like the at sign which is used in email addresses. in fact most of the symbols are wonky now. Ive tried rebooting over and over and nothing. This is what comes up when I type an apostrophe ä weird hunh...oh the question mark is now_!!! Ive been trying to figure out what to do, but dont know where to start. Can anyone help_ please, lol!

You are brilliant!! haha. That was it! My son was home for Spring break and had to do some translating from German to English.....who'da thought that?!?! Guess he changed it and forgot to put it back. I HATE when other people use my computer. Thanks for such a quick response...you just made my day, lol

Did you notice I have my ??? back? lol