Both the Lean and Agile worlds encourage and value learning by doing. The Scrum framework pushes teams to engage in an ongoing PDCA (Plan-Do-Check-Act) cycle to continually inspect and adapt how they work and how they develop software.
For Scrum teams, the end-of-sprint review is where they inspect the increment of work they created during the iteration and examine what they have learned about their deliverables. Based on this knowledge, teams can review their upcoming backlog items and adjust when they feel it is necessary.