Structurally, retweeting is the Twitter-equivalent of email forwarding where users post messages originally posted by others. This convention has no uniform grammar, although ‘RT @user msg’ is one common form. Because Twitter limits tweets to 140 characters, messages being retweeted must frequently be modified to accommodate the additional notation meant to indicate that the message is a retweet.
While retweeting can simply be seen as the act of copying and rebroadcasting, the practice contributes to a conversational ecology in which conversations are composed of a public interplay of voices that give rise to an emotional sense of shared conversational context. For this reason, some of the most visible Twitter participants retweet others and look to be retweeted. This includes users of all kinds, but notably marketers, celebrities and politicians