The document discusses usability testing, which involves testing a product on representative users to identify usability problems, collect data on user performance, and measure satisfaction, in order to improve the product design through an iterative process before public release. It covers planning tests, conducting tests by having users complete tasks while observers take notes, and analyzing the results to identify issues and make design modifications. The goal of usability testing is to create products that are useful, efficient, engaging, error-tolerant, and easy to learn for the intended users.