This has been discussed in previous threads. Cheaper cables use the shield as a conductor, whereas better cables use two internal conductors (+ and -) with a separate shield. In directional cables this shield is only connected (earthed) at one end, hence the arrow.
I'll leave the more technically-savvy guys to say whether this has an impact on sound quality.
I'll leave the more technically-savvy guys to say whether this has an impact on sound quality.