Depends on the teacher. Some teachers only use the iTalki Classroom, while others teachers might exclusively use Skype. Other options for teachers are Google Hangouts, FaceTime, QQ or WeChat. Of note, if your teacher only uses the free version of Zoom, you will have to reconnect after 40 minutes.

I am a nativer Chinese speaker，I want speak English fluently，if you want to learn Chinese，we can help each other.