Meaning: This sentence describes how the sound of laughter fills a quiet room.
Choice of Words: "Laughter's" is the possessive form of the noun "laughter", indicating that the echo belongs to laughter. "Echo" is a noun that refers to a sound that is repeated after the original sound has stopped. "Filled" is a verb that means to make something full. "Silent" describes the room as being quiet. "Room" is a noun that refers to an enclosed space within a building.