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Abridged: We used the fourth internal data release of the Gaia-ESO survey tocharacterize the bulge chemistry, spatial distribution, kinematics, and tocompare it chemically with the thin and thick disks. The sample consist on~2500 red clump stars in 11 bulge fields ($-10^\circ\leq l\leq+8^\circ$ and$-10^\circ\leq b\leq-4^\circ$), and a set of ~6300 disk stars selected forcomparison. The bulge MDF is confirmed to be bimodal across the whole sampledarea, with metal-poor stars dominating at high latitudes. The metal-rich starsexhibit bar-like kinematics and display a bimodality in their magnitudedistribution, a feature which is tightly associated with the X-shape bulge.They overlap with the metal-rich end of the thin disk sequence in the [Mg/Fe]vs. [Fe/H] plane. Metal-poor bulge stars have a more isotropic hot kinematicsand do not participate in the X-shape bulge. With similar Mg-enhancementlevels, the position of the metal-poor bulge sequence "knee" is observed at[Fe/H]$_{knee}=-0.37\pm0.09$, being 0.06 dex higher than that of the thickdisk. It suggests a higher SFR for the bulge than for the thick disk. Finally,we present a chemical evolution model that suitably fits the whole bulgesequence by assuming a fast ($<1$ Gyr) intense burst of stellar formation atearly epochs. We associate metal-rich stars with the B/P bulge formed from thesecular evolution of the early thin disk. On the other hand, the metal-poorsubpopulation might be the product of an early prompt dissipative collapsedominated by massive stars. Nevertheless, our results do not allow us to firmlyrule out the possibility that these stars come from the secular evolution ofthe early thick disk. This is the first time that an analysis of the bulge MDFand $\alpha$-abundances has been performed in a large area on the basis of ahomogeneous, fully spectroscopic analysis of high-resolution, high S/N data.

The Gaia-ESO Survey: Exploring the complex nature and origins of the Galactic bulge populations