Is StockX legit?

I've been hearing a lot about StockX recently, and I'm wondering if it's a legitimate platform to buy and sell sneakers and other streetwear items. Can you tell me more about their authenticity process and how they ensure that the products they sell are genuine? Also, are there any reviews or testimonials from customers that can help me make a decision? I'm new to this space and want to make sure I'm not getting scammed.