Today I was shocked by a (re)tweet linking to an infographic on the anatomy of templates in wordpress (you can find it here), so I decided to spin my own version for templates in MODX. Without further ado, but with great thanks to Jay Gilmore for providing very valuable feedback and preventing me from infringing MODX copyright and trademarks, here it is:
(You can click it to view the original sized one. Which is the same size if you're looking at this site from a proper computer, but may be easier to zoom in on from a mobile device of sorts).
That really sums it up, though I promise I'll do a proper tutorial on template best practices in the future :)