Story points are a relative unit for estimating the effort, complexity and uncertainty of a piece of work, compared with other work rather than measured in hours.
Teams usually estimate with a Fibonacci-like scale (1, 2, 3, 5, 8, 13) because bigger items are harder to estimate precisely. A 5 point story should feel about twice the effort of a 2 or 3.
Why not hours?
People are better at comparing sizes than predicting durations, and points stay stable when the team gets faster. Summed over a sprint, points give the team its velocity.
Planning poker
Each person picks an estimate privately and everyone reveals at once, which surfaces different assumptions early.
Story points in Starlex
Issues can carry story points, a project can turn them off entirely, and each person chooses whether cards show them. See sprint planning.