The document discusses Lean UX design sprints, which involve solving problems in 5-day intervals through activities like mapping customer goals, sketching solutions, deciding on a prototype, prototyping it, and then testing it with users. It provides an example of how Pocket used sprints to increase user activation. Sprints follow a process of understanding the problem on Day 1, sketching solutions on Day 2, deciding on a prototype on Day 3, prototyping on Day 4, and then testing with users on Day 5. Metrics like the System Usability Scale and Net Promoter Score are used to evaluate prototypes.