I don't describe them as classes because they're not formal, organized sessions which form part of a course, in the way that the ones I had at university were. 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 Context, as Barque explained rein #2, is the situation or circumstances hinein which the phrase is being used. https://youtu.be/T0zWXvhEQwo?si=wNc6ihu97ShtIl7u