On the night before his death, during the Passover celebration, Jesus instituted the communion supper for his disciples (Mt. 26:26ff; Mk. 14:22ff; Lk. 22:19ff; cf. 1 Cor. 11:23ff). The Lord's Supper consisted of two elements: bread and fruit of the vine.
The term "breaking bread" was a commonly used figure of speech in the antique world. It is a synecdoche (the part for the whole) representing a common meal. As the church began to practice the Lord's Supper, this common language was used to describe the entire communion celebration.
"Breaking bread" in the sense of the Lord's supper involves both components (cf. Acts 2:42; 20:7; cf. 1 Cor. 10:16-17). The breaking of bread that was associated with communion, though, must be distinguished from a common meal taken for physical nourishment. Sometimes we find this term in some contexts in which it clearly is a reference to an ordinary meal (Lk. 24:30; Acts 2:46; 20:11).