The student's tablet acts as a second screen, allowing them to interact with the presentation shown in the lecture hall. It allows them to annotate the slides, ask questions directly to the teacher, quickly flag slides that cause problems, solve exercises and respond to polls. All of this without interrupting the flow of the lecture.
The teacher receives direct feedback from the students during the lecture. He can monitor questions and flags, and respond to them directly or after the lecture. When the teacher asks students to solve or answer a problem, he can see how many people got it right, and perhaps clarify concepts that don't seem to have been understood.
Notes, questions and annotations are synced to the online environment, which also provides a communication and collaboration platform for the students and teachers. Additional material can be put online by students, helping others in understanding concepts, and even allowing the teacher to improve their lecture for following classes.