From Gibson.com:

Symmetrical scales are one of the most fun – and easiest to wrap your head around – ways of making harmonically interesting music without having to spend 10 years at music school (although if you can afford to spend 10 years at music school, please do, then tell me all about it so I may live vicariously though you, ’cos that sounds rad!). Two very well known exponents of the symmetrical scale are Eddie Van Halen and Dimebag Darrell. Darrell was quite open about borrowing the idea from Eddie, whose most famous example of the technique can be heard on his solo to “Ice Cream Man” from Van Halen’s self-titled debut. Eddie’s “Ice Cream Man” solo starts in the key of the song but quickly evolves into a bizarre, out-there-sounding tumble through cascading note flurries.

So what is a symmetrical scale, and how does it help you to rock? Well, it’s simply a “fake” scale made up