What is the true meaning of communion?

Audio Bible Study on1 1 Cor 10:16-20 16 The cup of blessing which we bless, is it not a communion of the blood of Christ? The bread which we break, is it not a communion of the body of Christ? 17 seeing that we, who are many, are one bread, one body: for we all partake of the one bread. 18 Behold Israel after the flesh: have not they that eat the sacrifices communion with the altar? 19 What say I then? that a thing sacrificed to idols is...