Planning Poker is a team-building activity that helps people come to an agreement as a group. Agile software development teams use it to estimate how long it will take to complete a specific amount of work.
The purpose of planning poker is to ensure that everyone in the development team shares their knowledge and actively participates in the estimation process. The activity is especially effective for projects with a lot of unknown variables and many areas of expertise that require several areas of expertise in order to acquire an accurate estimate.