Difference between Catholicism & Christianity?

Why are all Catholics Christian, but not all Christians are Catholic?

When you hear catholics speaks it’s almost the sense of tradition that is main reason for different practices. While Protestant groups are more for Bible based relationship with God. What are the main differences and if you’re Catholic what is it that you think the other side misunderstands about your direct beliefs? If you are Christian and don’t call yourself Catholic then what is a misunderstanding that you would like to point out to our Catholic brothers and sisters?

**Only using Protestant for reference, not touching on Orthodox christianity**