A story point is a measure of effort that expresses the relative difficulty of implementing a user story. You can use story points to help estimate how much work can be done in a sprint.
Story points are useful for relative measurement. A story point has no specific value in hours, or lines of code, or anything else. When you are estimating work, use story points only to compare one piece of work with another.
When you record a value in the Story Points field of an artifact, that value is added to the total story points in the planning folder that the artifact belongs to. You can then use that figure to support forecasting.