The basic idea of Leptogenesis is that the baryon-antibaryon asymmetry that we observe was produced through a lepton-antilepton asymmetry. This asymmetry, in turn, was produced, for example, through the decay of right-handed neutrinos.
The lepton asymmetry gets converted into a baryon asymmetry through vacuum tunneling processes known as sphalerons.
Leptogenesis is a possible solution for the baryon asymmetry problem of the standard model.