It basically uses the same methodology as the "regular" VIX, essentially a weighted index of implied volatility for at-the-money options expiring in about a month. You can calculate this data for any stock using option prices, but that's only practical on a close-to-close basis.
But the CBOE Apple VIX Index (VXAPL is the symbol) is updated throughout the day, so you can see how options prices may be changing.
For example, here's an intraday chart of the Apple VIX on Thursday, February 23, along with the stock itself.
The stock bounced around 515 for awhile, rose to almost 518, then dropped to around 510 at 1:30. Notice the movement in the Apple VIX. It did spike (that really high bar goes to 35.5, a great time to sell options if that's not errant data), then dropped to near 30 by the close.
Once whatever happened at the shareholder meeting got absorbed by the market and the stock recovered, the Apple VIX spent the rest of the day "relaxing" and drifting lower.
Does it make a difference? Sure. I'm watching the weekly March 2 485 puts which began trading on Thursday.
Around noon or so with the stock at around 516, they could have been sold for around $1.30. By the end of the day, with the stock near 516 again, you could have bought them back for around 85 cents. (I will note however, that they probably could have been sold for a lot more on that plunge around 1:30 p.m.)
Yes, you did have a half day's worth of time decay, and the weekly options don't necessarily follow any "VIX." But part of the difference is because of the collapse in implied volatility as measured by the Apple VIX.
Will the Apple VIX stay above 30? If the overall market holds up, I don't think so. Here's a look at a Bloomberg chart.
Post earnings, the Apple VIX settled near 20. Obviously, news trumps volatility predictions, but with the shareholder meeting now over, I think the Apple VIX will drop well below 30 - although there could easily be intraday spikes.
So VXAPL might be something worth putting on your watchlist if you're selling AAPL options.
Disclosure: I am long AAPL.