NPS is the Net Promoter Score: % promoters (9–10) minus % detractors (0–6). Benchmarks: above 50 is excellent, 30–50 is strong, below 0 needs urgent attention.
Email NPS surveys average 5% response rate, often skewed negative. Voice NPS calls average 30–40% response, with both positive and negative voices represented.
The qualitative answers. "three words about the product". Often deliver more product-roadmap signal than the score itself.