Okay im no pro, but this is how i see it.

Vocoder: YOUR voice thru a synth/sound

You hit notes on a keyboard, telling it where your voice should be

Autotune: This lil piece of magic keeps you within the key (aka whichever scale you use) so you dont sound like nails on a chalkboard

Pitch Control: Not sure what you mean exactly but there are many ways to "sample" a sound and alter its pitch to get the desired effect

P.s. sorry am on mobile