Hydration = water as a percentage of FLOUR weight (600g water in 1kg flour = 60%). It's the single biggest lever on what a bread becomes:
LOW hydration (stiff doughs) - tight, chewy, dense crumbs. Bagels live here, the stiffest dough of our bread module. Easy to shape, demanding to knead.
MIDDLE band (~60-65%) - the everyday zone: sandwich loaves, pav, Hokkaido, garlic loaf. Balanced crumb, manageable dough, forgiving shaping. Most of what home bakers make sits right here.
HIGH hydration (75%+) - the open, airy, hole-riddled crumbs of ciabatta and focaccia. Glorious results, sticky anarchic doughs - too wet for regular kneading, so technique shifts to folding and resting instead.
The religious intensity exists because hydration sets the RULES: how you knead, how you shape, what crumb is even possible. Read a recipe's hydration and you know its personality before touching flour.
Climb the ladder gradually - each 5% up teaches new hands. Jumping from pav to 80% ciabatta is how flour ends up on ceilings 😄