systemd is the new system and service manager for Fedora 15. It provides aggressive parallelization capabilities (zeroing serialization/sincronization), uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux cgroups, supports snapshotting and restoring of the system state, maintains mount and automount points and implements an elaborate transactional dependency-based service control logic. It can work as a drop-in replacement for sysvinit.
It is implemented around the notion of units. Units have a name and a type, whose configuration is in a file with the same name. There are several kinds of units: service, socket, device, others.