This excellent creation is a John Deere S790 combine harvester, and it comes from previous bloggee damjan97PL (aka damianPLE), who has forgone motorised features, instead combining wonderful old-school Technic mechanical functionality with modern System detailing to great effect.
A series of small cogs accessible on the outside of the model operate a variety of Technic functions, including the rotating raising/lowering and removable header, which can also be connected/disconnected from the drive wheels, and working rear-wheel-steering, plus the model features a swinging discharge tube, detailed cabin, and an opening grain hopper constructed from more traditional LEGO System bricks.
There’s much more of Damian’s excellent combination of Technic and System to see at both Bricksafe and Eurobricks, where a link to building instructions can also be found, and you can head there via the links above to bring in the harvest.