Think about all the apps you use in a day: Amazon, Facebook, Gmail, maybe Lyft or Uber. In China, some of those apps are banned. But it’s possible to use one app — WeChat — to do lots of things, like sending messages and ordering taxis. Facebook Messenger is trying to take on the same role in the U.S. Jennifer Pak, Marketplace's new China correspondent, gives us the lowdown on WeChat and talks about why there's no equivalent in the U.S. ... yet.