To be honest...I'm not sure what these terms mean?

Anyone care to explain?

Tx

With aftertouch you increase the pressure of a key which is already pressed down in order to add vibrato,increasing volume or other effects to the tone played.

"Initial Touch" means that the harder (or faster) you strike the keys, the louder the voice sounds. The timbre (character or quality) of the sound can also change, depending on the keyboard or voice you are using. For example, if you choose a brass voice and strike the keys hard, you might hear a "fall".

"After Touch" is like Rosetree said; once you strike the keys and are holding them down, if you push down harder, it will produce either a vibrato, a swelling in sound (where the volume gets gradually louder) or some other effect.

Hope this helps.

Tx. Helpful info.

You're welcome!

Aftertouch is a very cool way to introduce FX on a note you are already holding. I have a great patch on an old Roland JX-8P called "Soundtrack" where the aftertouch adjusts the analog filter and resonance that is just exquisite.

Aftertouch is so very important when you want to play with more expression.. the list is very small

-Aftertouch
-expression pedals
-half damper pedal
(offcourse you can use your switch pedals or even keyboard legato detection, for switching articulatiuons and stuff, but those are just swithces and not 0..127 values)

and this list allows you to add the expressivness of your sound, witouth taking your hands from the keyboards...

all those other controlleres (mod wheel pitch wheel/stick, knobs, buttons, sliders, drawbars, ribbon etc etc) requiere the use of a free hand..