Jesus was a radical. He spent his life invigorating Israelite customs and reinterpreting their laws. At the final meal before his death he did it again.
At a traditional Passover, Jesus told his followers that the wine was his blood and the bread his body. It sounds crazy on the surface, but they believed it because they knew him. His followers have continued the practice of that meal up to today. Following Jesus is not easy, it never has been, but when we share that meal we call communion we are mystically tied to Jesus and one another in a way unlike any other. Through his body and blood we receive forgiveness and strength to persevere. It may be a lot to swallow that simple bread and wine could do all that, but we believe it because we know him.