@Keti: I am not certain I understand your question.  I think that some teachers explain their purpose or teaching philosophy on their teacher profile page.  Some also write articles to share their views about language teaching and learning.  I wrote an article recently describing my approach:

http://www.italki.com/article/187/building-fluency-transitioning-from-language-knowledge-to-real-practice#.U76YGo1dUs0

Thank you very much for your detailed answer, Thaddeus. 

I only want to know, if Teachers from italki have plan for different purpose of their learners and if we can find out about it?

Language teachers (on italki or elsewhere online) are essential for most students because:

1. The student is studying in a location with limited access to native teachers of the language.

2. The student needs the flexibility of studying a language from their home.

Additionally, even if a student has opportunities to speak in their target language locally, they may not be able to get feedback about their language proficiency easily.  Here in the USA, I think that people are generally understanding when they are speaking with a non-native speaker.  Unfortunately, this often means that they are reluctant to correct or give language advice directly because they do not want to seem rude.

I think this can even effect lessons through Skype if you use video.  In my experience, teachers / tutors / language partners are much less likely to correct a person if they are looking at them than if they are just listening through an audio call.  This is why I prefer to give and take lessons through audio calls instead of using video.

Thank you very much for your comment, Vỹ. Of course, I guess that teacher would be better however I want to know agruments, why it's better.

the teacher is great and i hope that you would teach better. thanhk so much !