One of the main differences between the Catholics and Christians is how much they follow Jesus Christ. Catholics believe in the Pope which is something that Christians do not believe in. Christians will be free to reject some of the things that are written in the Bible. There are also instances when they have their own interpretation of what they believe is the truth.
For example, there are some Christians who are very strict about the things that the Bible says. Some of them would interpret them literally. This is the same with some Catholics too. Some of them do interpret the Bible in a literal manner.