After reciting the present definition of a substorm as incorporating both the driven and the loading/unloading process, this review will be addressed to two topics where major advances were made during the last two years: the downtail loss of substorm energy via plasmoid release and observational and theoretical studies of the substorm onset triggering mechanism. It will be concluded by pointing out the need of further studies, both observational and theoretical, of the substorm recovery phase and the poleward leap phenomenon.