Planning Poker is a technique used to estimate stories where each person is given deck cards similar to the adjacent picture where each card has a story point value on it. The story is presented by the product owner and the team get to ask any questions. Then simultaneously everyone shows a card representing what they think the estimate should be.
If there are differences they are discussed and then another round of estimating is attempted. After the second round if there is not a unanimous decision the highest value is given to the story.
This article is part of the our 100 Agile Tools & Techniques epic article based off the PMI list of recommended techniques and tools in their PMI-ACP certification syllabus.