Google app is one of the best app. You can find anything on this app. And one of the best thing about this app is that google manages all you work. Like google maintain records of you events, meeting etc. And google assistant this is awesome you can control you whole phone only by voice commands you dont have to unlock your phone just say ok google and this will unlock your phone.
This app work like a personal assistant. You can find anything and if like tommorrow is your train than dont know how but this app automatically reminds you about yout train with pnr.