Italki is MAINLY a marketplace that connects students to teachers who give paid lessons over the internet. Mostly, you learn by paying a teacher. Each teacher follows their own teaching method, it is not a standardized course. Italki is NOT a computer-based, automatic language teaching app like Duolingo. To attract traffic, Italki also offers a few other things, such as these forums. It is possible to use these forums to contact people interested in becoming "language companions." This is all completely informal and Italki doesn't monitor or check language companions. The forums are not the core of Italki. Everything helps, of course, but they are not really a way to learn a language.

According to my understanding, people meet other people virtually and chat in order to learn their preferred language. There are teachers who teach us our desired language too. Hope this helps you and if you want we can chat and learn together.