>What do people mean by this exactly?

Historically, “race” was a term invented to group/categorize people by language. From there it evolved into a reference of nationality. Most recently it has become a word to define an attempt to group people by physical characteristics.

So for example you associate race with ethnicity...the question is why? Ethnicity after all is a word to group people through nationality and culture, having nothing to do with physical characteristics...for example Irish is an ethnicity (in addition to just a nationality), but there are both black and white irish.