Back in 2014, Google launched "Offline First" YouTube app, which you are familiar with. YouTube first introduced offline mode in its main app. Then a few months back, it introduced a new "Smart Offline" feature in India to schedule video downloads during cheaper off-peak hours.
YouTube Go has been built to work where there is poor connectivity or none at all. Users will be able to choose their resolution while streaming or saving videos. If the users are on a poor or slow connection, choosing a lower resolution will speed up things up and consume less data. Even users on 2G network will be able to stream and save videos easily.
YouTube Go will let you preview a video's information by just taping on the thumbnail. Probably the best feature is that now a user can share videos with nearby friends without consuming any data. But the user will be able to share if the receiver must have the YouTube Go app.
App testers in India will soon be able to test it.
Via: YouTube (Blog)