The violin or classical vibrato is not something you'll find many players using these days, Holdsworth being one noteable exception. As mentioned in the vid, and exemplified below, it entails pulling and pushing the string along the length of the fretboard, thus lengthening and shortening the string. This will cause the pitch to either rise or drop in relation to the fretted pitch. And very subtle vibrato, which can be duplicated with any whammy-bar. However, it is still a good vibrato to know, and to have in your bag of tricks!