italki is free unless you want to hire a teacher from the Language Teachers section. Then you need to pay whatever price the teacher sets. Many of them offer free trial lessons. You can post your language (or other questions) here in this Answers section. You can find a language partner to practice or have a language exchange with under the Language Partners section. The Knowledge section includes all sorts of reference materials and useful links for the language you want to study. The Groups section is a place where you can form a group with other members around some common theme, both language-related and non-language related.

交流是免费的，除非你想上某个老师的课程，同时，我也找不到社区现在在哪里了，可能中国版的已经没了吧我猜