Earmuffs are two soft pads, one for each ear, joined by a band over the top of your head. You wear them in cold weather so your ears stay warm. They sit on the ears; they do not go inside. The word is almost always plural, like a pair of earmuffs. They are not earphones: they do not play music. Though actually, some workplace “earmuffs” look the same but are for loud noise, not for cold — those are hearing protectors. In everyday talk, especially in winter, earmuffs means the warm pair.