It is not broken in the sense of creating smaller pieces of protein - that occurs during the malting, and mashing steps. If you are using extracts, then you have no control over this step.
I suspect it is called break after the way a cream sauce will "break" into an oil phase and a water phase as it sits in the leftover container in your fridge. The "clear" wort becomes chunky, or broken, as the proteins coagulate.
What everyone has control over is the precipitation of protein during the boiling phase (hot break) and the cooling phase (cold break). The precipitation reaction is the same that occurs when an egg is cooked. The liquid proteins lose their normal shaped and then clump together to form a delicious food item. The same thing happens in a boiling wort. Some of the proteins unravel (denature) and then they clump together into hot break. Still others will remain dissolved even at boiling temperatures. These proteins however when subject to a rapid temperature change will now form clumps. If the wort is cooled slow enough, some of these will slowly re-fold into their normal shape and remain dissolved (and will contribute to haze). In general, the better both the hot and cold break, the less chance you have of getting haze
