The “what” of Holy Communion refers to the 2 elements in the communion meal; the bread and the cup. The bread symbolizes the broken body of Jesus and the cup symbolizes the shed blood of Jesus. The physical body of Jesus was broken for the healing of our physical bodies. The blood of Jesus was shed for the healing of our spirits; spiritual healing is the forgiveness of sins, the removal of our old sin nature, and the impartation to us of eternal life, which is the life and nature of God. (See 1 Peter 2:24)
The ultimate goal of your existence is to glorify God. The “why” of Holy Communion is the reason we live for the glory of Jesus. “Why” is a question that determines motivation. As believers, our primary motivation should be to live for the glory of Jesus because of what He did for us. The “why” of Holy Communion is the reason we live for the glory of Jesus. The degree to which a person appreciates what Jesus did for them is the degree to which they will live for the glory of Jesus. The degree to which a person appreciates the love and forgiveness the Jesus died to give them is the degree to which they will walk in love and forgive others.