Chat, gab, chatter, patter, prate, prattle, babble, gabble, jabber, gibber denote to emit a loose and ready flow of inconsequential talk or as nouns the talk so emitted.
To chat is to talk in light, easy, and pleasant fashion.
To gab is to talk trivia glibly and long, often tiresomely.
To chatter is to talk aimlessly, incessantly, and (often) with great rapidity.
To patter is to speak or repeat rapidly and mechanically or glibly and volubly often without much regard to sense.
To prate is to talk idly and boastfully. The word is often specifically used in reproach implying platitudinous or fulsome boasting or a readiness to talk at length about things of which the speaker is really ignorant or has only superficial knowledge.
To prattle is to talk like a child (as in artlessness and freedom or sometimes in lack of substance and sense).
Babble, gabble, jabber, and gibber basically imply a making of sounds suggestive of speech but lacking the meaning content, intelligibility, and articulateness of normal adult human speech.
As applied to human speaking or speech all four terms are somewhat derogatory and especially suggest lack of clarity in both articulation and content.