In college, like larger universities they usually talk about the basic important stuff because the professors have alot of research/other activities outside of a 50/hr-and-half min class. But its your responsibility to teach yourself the rest. I am serious about this... I know it sounds strange but most classes will not spoon-feed you information. Even in high school, you should be getting into the habbit to actually look at your books and have it supplement your normal class. They can only show you so much. If there is something you dont understand, talk to classmates or the teacher before/after class (unless you get a chance to ask in class).
Pretty much what 2c said...
2cthe earlier you get in the habit of relying on books instead of teachers the better tbh