Application initialization My video "Under the hood of Magento": http://www.youtube.com/watch?v=M10RR9acNE8 (watch in 1080p)
Front Controller These articles both cover in greater depth how the Front controller is initiated and how routers are selected. http://www.andreiboar.com/magento/magento-front-controller/ http://blog.belvg.com/magento-front-controller-pattern.html
URL rewrites These articles describe how url paths are formatted, where theyre located, and how theyre used by routers. As well as ... dun dun dunnn .. how the catalog url rewrite indexer works.