Question

What is poker planning in Agile estimation? What does it estimate? Why is it effective?

Answer 1

Planning poker in agile used to be very effective tool for estimating the relative size of project tasks. 
It allows the whole team to understand what work is coming up, and have their say on how simple or complex the tasks are.

Poker is an agile estimating and planning technique that is consensus based. To start a poker planning session, the product owner reads an agile user story or describes a feature to the estimators. 
Each estimator is holding a deck of cards with values like 0, 1, 2, 3, 5, 8, 13, 20, 40 and 100, which is the sequence. The values represent the number of story points, ideal days, or other units in which the team estimates.The estimators discuss the feature, asking questions of the product owner. When the feature has been fully discussed, each estimator privately selects one card to represent his or her estimate. All cards are then to be shown at the same time.
If all estimators selected the same value, that becomes the estimate. If not, the estimators discuss their estimates. The high and low estimators should especially share their reasons. After further discussion, each estimator again selects an estimate card, and all cards are  revealed one more time.
The poker planning process is repeated until consensus is achieved or until the estimators decide that agile estimating and planning of a particular item needs to be deferred until additional information can be acquired.
Poker planning in agile mostly used to estimate effort or relative size of development goals in software development.
The cards are revealed, and the estimates are then discussed.
Planning poker in agile used to be very effective tool for estimating the relative size of project tasks. 
It allows the whole team to understand what work is coming up, and have their say on how simple or complex the tasks are.