The not-allowed cursor, often represented by a circle with a diagonal line across it, serves as a visual cue to users that a certain action is not permitted. This cursor is particularly useful when hovering over elements that are disabled or inaccessible. For example, you might see this cursor when trying to drag a locked file or interact with a grayed-out button. The not-allowed cursor's role is to inform users that their intended operation can't be completed, reducing confusion and guiding them towards valid interactions.