Natural Harmonic: On these you can place a fretting finger (left hand) over a fretwire (3rd, 5th, 12th, 24th are the easiest to use) and then pick the string to create the "chime" type effect.
Artificial/pinched harmonic: With this one you'd push down a fret with your left hand and then use your index finger of your picking hand to go over the fretwire 12 frets above that note to create a "chime." An example of it is in my lessons where I show how to play the NBC chimes using these harmonics.
ex. (lh = left hand frets 2nd fret)
(rh = right hand - use index over 14th fret's fretwire, play string with middle/thumb, if hyou're using a pick that is)
L.H. R.H
e |---2-----(14)-------|
Hope that helps.
Here's a link to the NBC trick:
http://www.guitartricks.com/lesson.php?input=7530