Delay copies what you play, and plays it again a certain amount of time later, it delays it. You can set the time.
Reverb basically gives the illusion that you're in a larger room so the notes blend together more and are less clear. People use it to cover up sloppy playing alot.
I think chorus has something to do with rapid vibration so it gives a weird effect.
CHORUS:
"an audio effect used to "expand" or "thicken" a sound by playing multiple versions of the input signal with slightly different delays and changes in pitch simulating an ensemble of the input sound."
"An electronic device that can split a signal, mildly shifting the pitch and timing of one part, then mix it back in with the original signal. The effect is roughly like several people (they’re the chorus) playing the same part at the same time. Solstice has effects loops to allow convenient interface with chorus effects."
"A special effect in which a single sound source is made to sound like several, through the use of time delay and detuning. Delaying the input by a slowly varying time between 15 and35 milliseconds and mixing the dry input signal back in, a wavy, multiple-voice effect is achieved. It's also possible to feed a portion of the signal back into the input."