The description for "init" on http://www.busybox.net/downloads/BusyBox.html is not helpful: "Init is the parent of all processes". Which "init" it implements would be more helpful: "init implements a subset of the SysV init mechanism". A pointer to the description of /etc/inittab" would be more helpful (but that doesn't exist either). What arguments does it take? How are then entered (I know - it depends ...)
$ busybox init --help BusyBox v1.25.0.git (2015-12-30 16:53:51 CET) multi-call binary. Usage: init Init is the first process started during boot. It never exits. It (re)spawns children according to /etc/inittab.