String skipping
String skipping is a guitar-playing technique that is used mainly for solos and complex riffs in rock and heavy metal songs.
Explanation of technique
String skipping is a method of achieving a guitar sound that is different from more traditional solo riff styles. In more traditional styles, the guitarist will often play several notes on one string, then move to the adjacent one, improvising on the fretboard in a melodically linear manner. In string skipping (as the name implies), a string is often skipped during the riff. Essentially, this technique is used to introduce larger intervals than are usually common in guitar melodies, thereby creating melodic interest.
Example of "traditional" solo riff style
Example of string skipping style
Notice that not every note played represents a string-skip; it is usually the case that string skipping is interwoven with traditional adjacent riffing. Playing the above example, one can hear the difference; the string skipping makes the solo stand out.