Covenants are promises. Communion is about saying Yes' to God's promise to love us and care for us. When we say yes' what we really mean is that we will attempt to serve and follow God's way as best we can. When we take the communion elements and eat them, the love of God becomes a part of us, and we respond in love and service. Just like regular food gives us energy to live, communion gives us special, or spiritual energy.
Communion is also a mystery.
We don't know everything there is to know about it, or about God's love and care. The prayer we have as part of the communion service can seem quite long, but each part is an important step in remembering, or giving thanks to God for all of God's blessings. This prayer is commonly called the Great Thanksgiving. We might like to know that Christians have used this dialogue, in many different languages, of course, for almost 2000 years. And that's a LONG time.