Planning poker is a collaborative estimation technique used in Agile software development. Team members use a deck of cards, each displaying a number that represents the effort required to complete a task. During a meeting, the team discusses a user story, and each member selects a card in secret to indicate their estimate. After everyone reveals their cards simultaneously, the team discusses any discrepancies in their estimates. This process encourages open communication and helps the team reach a consensus on the effort required. Ultimately, planning poker promotes better understanding and more accurate planning for upcoming work.