CMU is unusual in being a top-tier school with that arrangement. They actually have three tracks of professors. There's still a "regular" professor with the usual research/teaching mix. Then there is a "teaching" professor, which is also a tenure-track/tenured position, but judged mainly on teaching with research secondary; they are not expected to bring in as many grants or publish as many papers, but teach more courses per semester and are judged more strongly on their teaching quality. And finally there's a "research" professor, which deviates from regular professor in the other direction: they're judged mainly on research, with a lower teaching load, but a higher expectation for grants and publication output.
CMU is unusual in being a top-tier school with that arrangement. They actually have three tracks of professors. There's still a "regular" professor with the usual research/teaching mix. Then there is a "teaching" professor, which is also a tenure-track/tenured position, but judged mainly on teaching with research secondary; they are not expected to bring in as many grants or publish as many papers, but teach more courses per semester and are judged more strongly on their teaching quality. And finally there's a "research" professor, which deviates from regular professor in the other direction: they're judged mainly on research, with a lower teaching load, but a higher expectation for grants and publication output.