Learning in small groups has ancient traditions from the foundations of Western Philosophy in Greece, to the culture of ancient India and in the traditions of ancient Chinese and Japan. Indeed the roots of the world’s great religions, started with a teacher interacting in small group classes.
The key component of learning in online groups in general is that the social interaction between students challenges them, promotes active learning and opportunities to use language in context as it occurs naturally.
Group classes are classes where you have one teacher and a group of students. It's that simple!
In summary, Collaborative Learning:
While it is true that 1:1 tutoring is more effective than large, passive group classes, research indicates small collaborative groups result in the best outcomes, this is particularly true of language education due to the strong benefits of Social Learning.