Students gain first exposure to new material outside of class, usually via reading or lecture videos. This means that students are doing the lower levels of cognitive work (gaining knowledge and comprehension) outside of class.
Then use class time to do the harder work of assimilating that knowledge, perhaps through problem-solving, discussion, or debates. They are focusing on the higher forms of cognitive work (application, analysis, synthesis, and/or evaluation) in class, where they have the support of their peers and instructor.