It's a Loop Piled carpet, it's also called Berber carpet.

Lovely carpet but not dog toe nail friendly.

You're right Theresa, the reason why is that the looped style of Berber is a perfect design for cats and dogs to snag their claws and cats sometimes treat it as a scratching post. This results in snags, which can permanently damage the carpet.

What type of carpet would you recommend on the staircase as a runner?