Standard VHS audio is put on a narrow linear track and has its own tape head, separate from the video signal, which is read with a diagonal spinning head, as Farview described earlier.
Hifi VHS puts both signals on tape through the diagonal spinning head but keeps them separate by other means which someone else could explain better than me. It eliminates the typical wow and flutter type problems common with standard VHS audio and allows higher fidelity since it imitates a very high tape speed.
The problem Farview mentioned is somehting I'm not familiar with though.
