Never heard of hydration before

To add a bit to what Dan said (love your book, Dan) -- and maybe you don't need this, Vonilda -- you may see terms on TFL like high hydration or low hydration. There's no defined point where that breaks (as far as I know!), but as general terms they are descriptive. High hydration doughs -- those with a high percentage of water in relation to flour -- will result in very different loaves when compared with loaves with low hydration. For instance, if you're making a French baguette you're aiming at a much higher hydration level than if you are making bagels.

Also generally speaking, doughs with different hydrations will require different techniques in the making.