The aim of embarking on a silent retreat is to curb idle chatter or what is referred to sometimes as "unprofitable talk". Idle talk prevents one from being mindful.
There is a list of idle talk in the Digha Nikaya, iii, 36-7. It is the story of the Band of Six who had the habit of rising up in the night before dawn and donning wooden slippers, parade up and down in the open air, chattering in shrill loud tones, hawking and spitting, and talking all manner of idle babble, such as: talk about kings and robbers and ministers of state; talk about armies and of fear, tales of fights; talk about food, drink, clothes, beds, lodgings, flower-garlands, scents, kinsfolk, and carriages; about villages, suburbs, towns, provinces, women, and soldiers; gossip of the streets and wells, and tales of ghosts; all sorts of talk; about the world and the Ocean; of things existent and non-existent. And while so doing they trampled to death all sorts of insects. Moreover, they distracted the brethren from their meditation.
(N.B. The Band of Six were later expelled from the Order)
The antidote to idle chatter is of course "right talk" or the Aryan Speech. The Aryan is "a wise man, fain of speech, He knows the proper time, and speech concerned with righteousness and practice of right talk."
(Anguttara Nikaya, i, 199)
To counter idle chatter, one can go on a silent retreat, or better still, practice "the Aryan Silence". The Aryan silence is a method to suppress discursive thought. It is "a state of internal calm of heart, concentrated on its object, born of mental balance, a state of zest and ease".