I like the community features the most. You can post discussion topics, as you just did now. You can also ask questions about language or culture. My favorite thing about italki is the notebook feature. You can write an entry about anything you’d like, and a native speaker will correct it for you. It’s great for writing practice.
By the way, italki does not like when people use the discussion and question/ answer forums to find language partners. There’s a whole other section of the website to help you with that. But as you’ll see, a lot of people don’t follow that rule. I’m only bringing this up because you’re asking about italki’s uses and features.