Allright, I will explain this in laymans terms,
A natural Harmonic is when you touch a string over either the 5th, 7th, or 12th fret, and pluck the string, anyone fucking around on a guitar can produce this Harmonic, an Artificial harmonic is when you tap the string with your index finger of your picking hand while at the same time plucking the string, a pinch harmonic is when you hold the pick between your thumb and index finger and while you play a note, brush it with your thumb, this last one takes practice but is useful,