What are story points?
Story points are a format to express estimates on how much developer time it will take to complete a user story. There is no unified definition of how big a story point is, as that varies between teams, and they are meant to be a rough and not an estimate measure, but for many teams a story points come to mean roughly one day of work for one developer. Generally, the number of story points required to complete a user story is driven by the scope of the user story, how demanding acceptance criteria are set, and the amount of uncertainty.
Story points can be used during agile planning in the development part of the product management process.