As per Google Apps for Education:
Google Classroom is a powerful tool which educators can set up in minutes. With Google Classroom, they can manage assignments and communicate with students in one convenient place.
Teachers and students can work anywhere, anytime, and on any device. Google Classroom seamlessly integrates with other Google tools and helps educators refresh their curriculum with integrated education apps.
Additionally, educators can provide instant feedback and it also helps free up educator time so they can focus on what they do best: teaching!