I am confused what the differences are in Europe, but what about when the Europeans colonized Americas and Africa, which branches were most present??
It kind of depends where in the Americas you’re talking about. The British and French were in Northern America and Canada while the Spanish and Portuguese were in the southern part of N America, central America, and S America.
As far as Africa goes, just check out a map for the Scramble for Africa: https://www.google.com/url?sa=i&url=https%3A%2F%2Foriginalpeople.org%2Fscramble-for-africa-par%2F&psig=AOvVaw24vduMQ25HnXirVnI_RyHN&ust=1590095751429000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCLCSx7auw-kCFQAAAAAdAAAAABAN
“Christians” refers to those who follow Christianity, in its many forms.
Catholics practice a form of Christianity that’s different from the Protestant form. (For example, Catholics worship Saints and hold Mass whereas Protestants do not.)
Protestants and Catholics got into religious wars in Europe over the differences.
Orthodox is another branch of Christianity, usually found in Eastern Europe.
I hope this helps!
You can find some more information here: https://app.fiveable.me/ap-hug/unit-3/diffusion-of-religion-language/study-guide/5bKdwOUX9QXwx6auK4uw