What is the difference?

[maggieNomar 0]

After we were married and it was recorded at the courthouse, we went in person to the courthouse and paid for 3 certified copies of our marraige certificate. Each one was stamped by the clerk.

Kev_n_Jena

That is what we sent as well, the certified copy with the stamp on the back. While the USCIS may have a policy about it, you never know what kind of officer you will interview with/i.e. their interpretation so better to be over prepared, IMO. I would not take just a copy from the copy machine. I had to get a certified copy of my divorce decree even though I had the original and a copy of it with me.

[rustynail74 0]

I would say as long as you have the original and you bring two or so copies with you for the Immigration Officer, you are well set. IO can check your original certificate and will keep the copy for his/her records. You really don't need to bring a certified copy which is required only in the absence of original (for the viewer)