On the site Marsha linked to, check out the link for construction types. It explains what a frieze is pretty well there. I like the friezes as a nice alternative to berbers.
If it didn't smile, then it sounds like you have a really dense berber. It will probably perform pretty well on stairs, as long as you aren't getting smiles (which detract from the appearance more than anything). Definitely read the warranty brochures about stairs, though. I did a search to varify and found more than one mention that carpet installed on stairs is excluded in many instances. That doesn't mean that the installer or the retailer won't offer a warranty, though.
One thing I don't like about the site, though, is it doesn't go into PET Polyester on the page about fiber. PET Poly is made of recycled soda bottles and is much more durable than virgin polyester, second to nylon in memory and texture retention.