Over simplification inbound.

Race is not the same thing as ethnicity. In the context of my middle American high school, we were all racially 'white.' There was ethnic variation between my classmates. I have an ethnic background based in the culture of a group of Finlanders who came to the US at the turn of the 20th century. A friend of mine is the first born son of a Ukrainian immigrant who came over here when things started getting squirrely after the fall of the Soviet Union. If there was a picture of the two of us, it would hardly be labeled 'Diverse' and our upbringings and culture were vastly different.

In this case, 'white' is the national census sub-group we both fall under. We are racially similar, almost identical. My friend has been working hard at getting rid of his accent because it was giving him difficulties in college and more when he was looking for work. Racially similar, ethnically different.

That of course is limited to this example, and other definitions of both 'race' and 'ethnicity' exist. In the 'ethnicity' field here at the hospital, you can check hispanic/latino, non-hispanic/non-latino, or other. That is different from the 'race' field, which has all the census favorites in it.