Upstart is an event-based replacement for the /sbin/init daemon which handles starting of tasks and services during boot, stopping them during shutdown and supervising them while the system is running.

It is being developed for the Ubuntu distribution, however is intended to be suitable for deployment in all Linux distributions as a replacement for the venerable sysvinit package.

From the article:
For years, most Linux distributions have been using an init daemon based on the one found in Unix System V. The init daemon is spawned by the kernel itself, and tasked with booting the rest of the system, starting all other processes, and taking care of them when they need to be stopped or when they die. While the System V init setup has worked well for Linux in the past, it hasn’t aged well — which is why we’re replacing the aging init system with Upstart in Ubuntu 6.10, codenamed Edgy Eft.

Read more at Linux.com