Pose that question to 10 people and you will get 20 different answers. For product testing, performance falls into a few categories. The one that is top-of-mind for most people is “How well does the product perform or function?” Once people know a product will do what it is intended to do (function), then several other questions arise, e.g. How long will it function?, How well will it function?, Under what conditions will it operate?, How easy is it to use?, How well is it put together?