The Eucharist (Communion). Transubstantiation is a big word that means that the bread and wine at Communion literally become Christ's body and blood. When I was an evangelical, this was one of the most difficult concepts for me to grasp as I explored and studied Catholicism. Frankly, I thought it was a bit hokey until I started reading explanations from the Bible and church fathers. The most powerful is in John 6:25-71 when Jesus told those gathered that they had to eat his flesh and drink his blood to have eternal life. When the disciples questioned him, Jesus confirmed that he had meant what he said. Some of his followers were so turned off by the idea of eating Jesus' flesh and drinking his blood that they abandoned him. Catholics believe that if Jesus had actually meant for the elements to be merely symbolic, Jesus would have gone after the deserters and reassured them.
Bridges of mutual understanding
Let's be clear: I don't expect to convert anyone via this article (my mom, by the way, now will attend mass with me—but she remains firmly evangelical). Instead, my intention is to help create some bridges of understanding for evangelicals about Catholics—bridges that go two ways. Having participated in both fellowships, I can attest we both can gain much from each other. Catholics could use evangelicals' help in building community (small groups, for example) and approachability (such as making the mass more accessible to newcomers). Similarly, evangelicals might look to their Catholic brothers and sisters for how to appreciate the Christian church's history and how to incorporate meaningful traditions in worship.
If Christians want to follow the Great Commission (Matthew 28:16-20) and win people for Christ, we need to band together. Does that mean we ignore our differences and pretend they aren't there? No. But rather than fixating on our differences and making enemies of each other, through accurate mutual understanding we can build on our shared convictions and can together be powerful messengers of the gospel.