What does this mean?

I was reading up on Upenn professors on the school website and I came across this "…Penn is unique in one notable way: All of our faculty teach undergraduates. That’s pretty unheard of. We don’t hire faculty, no matter how brilliant, who aren’t interested in the teaching mission of the College of Arts and Sciences. " What exactly do they mean by this? Don’t faculty teach students at all universities? What’s so special about this?

No. At some universities, some faculty only teach grad students. Some faculty only do research.

^Ditto.

Faculty teaching students is not that common, especially for the major research universities like Penn. So the fact that at Penn every class is taught by a professor is indeed quite special. For example at Harvard many classes are taught by TAs who are grad students.