Review-wise: It's not immediately evident -- from just reading the front page -- what the gameplay consists of. I get that it's about taxis and on real world maps. But what do I do? How do I win? Or at least rack up some sort of higher score than my friends? What's my goal? Or is this purely a sandbox?

The page tells me that I can "Build things," "Run [my] company with friends," and even "drive on a real map" but it doesn't make it clear how do I any of these things or why they'd be fun apart from any initial novelty...

Some advanced game features require paying, and advertisement shows up eventually. It's a standard model for these sorta games.