NPS stands for Net Promoter Score. It's supposed to get a sense of % favorable - % unfavorable and leaving out the middle.

I've seen this at many companies and its one of my biggest pet peeves. Almost nobody uses it correctly. They don't net anything. They take the average. It's not clear at all why it's any different from any other score. I think most people think its some sort of collection or measurement thing rather than a calculation on the data. I hate it. Reeks of innumeracy.

Not that it really matters if you use average vs. nps...