What causes the creaking sound in stairs and how can it be fixed?

The creaking sound in stairs is typically caused by loose or worn-out components, such as the treads or risers rubbing against each other. To fix it, you can try tightening any loose screws or nails, adding shims or wedges to stabilize the stairs, or applying lubricant to reduce friction. If the problem persists, it may be necessary to replace the damaged components.