In this post, we get a fantastic, deep dive breakdown of the Package and Program process inside of Configuration Manager 2012.  This is one of the most detailed articles I have read to date.

“I will describe the process from the time the Configmgr admin creates the package in the console up until the time when the newly created package a program(s) are distributed, distribution of a package warrants its own article at this depth.  Specifically I will show how the different Configmgr components are involved, what logs are written to, what you should see in the logs, as well as some additional details like the inboxes, files created for processing and additional details that are not typically discussed.” – Anthony Clenendon

See the post here:
https://www.itsdelivers.com/newsroom/package-creation-internals-in-ConfigMgr/

See his full blog here:
http://configmgr.com/