Swing Feel: As opposed to “straight time”, giving a rhythm a swing feel most commonly implies lengthening of the first half of a beat and shortening the second half. So where a straight count of eighth notes in 4/4 time might be verablized, “dah-dah dah-dah dah-dah dah-dah,” a swung count might be, “daah-dit daah-dit daah-dit daah-dit.”
Harmonics (in guitar playing): Playing a note in such a way that some of the harmonic tones are cancelled. These can be broken down into several types, including: natural or open harmonics, artificial harmonics, tapped harmonics, and pinch harmonics (squealies). See: Guitar Harmonics
Natural or Open Harmonics: Picking or plucking an open string while lightly touching one of the node points on the string, quickly releasing the touch just after the string starts to vibrate. There are node points in many places along the neck, however typically the 12th, 7th, or 5th fret are the most used and easiest to make ring.
Artifical Harmonics: Similar in concept to natural harmonics, artificial harmonics are played by fretting a note and lightly touching and releasing the point 12 frets up from the fretted note while picking or plucking the string. For example, if the second fret is pressed, the harmonic would be played at the fourteenth fret. Theoretically, any of the other nodes of the fretted string would work, however in practice they are more rarely used and somewhat harder to play.
Tapped Harmonics: Tapped harmonics are similar to artificial harmonics in that the harmonic is played typically twelve frets up from a fretted note. However, rather than playing the string while lightly touching the twelfth fret up, the fret is “tapped” with the picking hand. This often results in both the note at the twelfth fret up being heard as well as the harmonic.
Pinch Harmonics (Squealies): Pinch harmonics are played by letting the thumb or finger of the picking hand lightly touch the string after the plectrum has picked the string. These can be done at several nodes, most commonly at about the location of the neck pickup on an electric guitar. These harmonics typically result in a very high-pitched sound, leading them to be called “squealies”. Because of the location near the end of the string, the lack of consistent references (i.e. no frets) to use as a guide to the node points, and the overall trickiness of touching the string lightly at the right time with the thumb or finger while picking, pinch harmonics require significant practice to play consistently well.
The Dimebag Squealy: The “Dimebag squealy” is an open harmonic played in a specific way using a vibrato arm (aka “whammy bar”) to get more of a pinch harmonic sound. It is somewhat difficult to explain. Rather than picking the string, the fretting hand “flicks” the string near the point of the harmonic node. Then, the whammy bar (most often a Floyd Rose style) is used to significantly loosen the string. Finally, while letting the whammy bar up, the fretting hand lightly touches and releases the harmonic node. The note becomes a squeal, and the whammy is used to vary the tone/pitch as desired. Here is a video of Dimebag Darrel himself explaining the technique: https://youtu.be/nGzxKNz3cgc
Open Chords: Chords played with some open (non-fretted) strings. Usually the first chords learned when learning to play guitar.
Moveable Chords: Chords played with no open strings. Thus, the shape is moveable to other locations up and down the neck to create other chords.
Barre Chords: A special group of moveable chords where the index finger creates essentially a capo-like backstop and otherwise using shapes similar to open chords.