Group schemes and buildings of exceptional groups over a local field.: First part:: the group G2

We give an explicit Bruhat-Tits theory for the exceptional group of type G(2) over a local field. We describe every construct concretely in terms of lattices: the building, the apartments, the simplicial structure, and the associated group schemes. The appendices discuss analogy with symmetric spaces and the symmetric space of the real or complex G(2).