Civil war soldiers in red uniform w/ turban?

I recently saw a picture (I believe it was the Battle of Fredericksburg) in my History Textbook, and in that picture was detailed a group of men with rifles advancing against Confederate gunfire, wearing red pants and a turban. I’m pretty sure this wasn’t standard Union uniform during the Civil War. So, who exactly were these guys, if they even existed?

Zouaves.

Rarely does one word so completely answer the question.

Sounds like a Zouave unit, who copied the uniforms of the French Zouave infantry.
It was something of a fad at the beginning of the Civil War.