From [xlab : a mac os x weblog]:
This fine article appeared on kernelthread.com last week, and I’ve only just finished reading it. It’s a well researched and incredibly thorough article which covers just about everything you might need to know about the technical side of Mac OS X.
The article was originally written for Linux users interested in switching, but, despite this it’s well written and doesn’t overwhelm you with tech-babble and bombard you with acronyms. Worth reading over lunch with a bacon and brie sandwich and a big mug of tea.