Go here for a simple explanation:
http://www.jahitchcock.com/search.html
Many of our veterans' records were destroyed in a fire in the 1950s (I think) and so much has been lost. If you have any pictures of your relative's dress uniform, you can look at his medals to figure out where he fought (which theatre, landings etc.).
Send me a private message if you need any more info. Would be glad to help. WWII history is a passion of mine. I'm no expert, but probably know a bit more than the average Joe.
Good luck.
bump
Thank you - I do have a number of pics of him at home that I took when we cleaned out his apartment. I also have a letter he wrote his sister when he was still stationed in the US which might have some unit info on it. I'll see what I can dig up and send it to you - or just post it on this thread. It's astounding the length of time that generation kept silent about everything it lived through...it's about time to get the stories out.