Upcoming Test

I'm not to confident that I'm going to do well on this test because I don't really truely uderstand most of it. I try to understand but sometimes I just don't get what we are talking about, I listen in class and I try to participate as much as possible but I don't know I just have a hard time understanding your type of science you teach us. I don't really know what to study like I know that we are suppose to study the weather and stuff like that but what specifically do we study??? I'm kinda worried that if I don't pass this test I'm going to flunk this class, will this effect our grade one hundred percent??