Rundown used in a sentence

Rundown in a sentence as a noun

The Wikipedia article has a nice rundown on how a US Senator's name ended up thus: 'The word santorum, as defined, has been characterized as "obscene", "unfit to print", or "vulgar".

Can anyone give a quick rundown of the different init systems?For the most part it can get confusing for a non day to day system administrator when I am trying to get a program to "run on boot".