:According to Lennart Poettering, the developper of systemd:

::''"systemd is a '''system''' and '''session manager''' for Linux, compatible with SysV and LSB init scripts. systemd provides '''aggressive parallelization''' capabilities, uses '''socket''' and '''D-Bus''' activation for starting devices."''

:In Simpler Terms:

:'''systemd''' is a more efficient method of controlling processes. It has the flexibility to start services in parallel, and have them communicate with each other, even if they are restarted (respawned). This is particularly useful for system administrators to temporarily service or update services without affecting the other dependent services.