A story that at this point in time, is impossilble to be done

The defect does not affect functionality or data. It does not even need a workaround. It does not impact productivity or efficiency. It is merely an inconvenience.

The defect affects minor functionality or non-critical data. It has an easy workaround.

The defect affects major functionality or major data. It has a workaround but is not obvious and is difficult.

The defect affects critical functionality or critical data. It does not have a workaround.

The backlog is a list of rough ideas for the product that still need to be refined. They are stalled for future refining.