Story points are a unit of measure for expressing an estimate of the overall effort that will be required to fully implement a product backlog item or any other piece of work.
When we estimate with story points, we assign a point value to each item. The raw values we assign are unimportant: Some teams use a modified fibonacci sequence (1, 2, 3, 5, 8, 13); others use a doubling sequence (1, 2, 4, 8, 16).
What matters are the relative values. A user story that is assigned two story points should be twice as much effort as a one-point story. It should also be two-thirds the effort of a story that is estimated as three story points.
Instead of assigning 1, 2 and 3, that team could instead have assigned 100, 200 and 300. Or 1 million, 2 million and 3 million. It is the ratios that matter, not the actual numbers.
One of the main reasons story points are so valuable is that they allow team members with different skill levels to communicate about and agree on an estimate. Instead of arguing about how long it might take each team member personally to do something, teams instead can quickly say that this user story is about twice or three times as much effort as that user story. With story points, it’s all relative.
