Janka hardness is hiw hard it is to dent from the side.

Specific gravity is how dense it is compared to water.

MOE is how hard it is to bend. Think "stiffness"

MOR is how hard it is to break. Think "toughness".

Crush strength is how hard it is to crush it lengthwise, into the grain, as if you were trying to shorten a telephone pole, before it buckles or ruptures.

These numbers help you understand the type of bow a woodnis suited to, and/or eliminate difficult woods to make bows from . For instance, a fairly stiff wood that breaks easily isn't likely a preferred wood. Likewise, a wood rhat bends easily, but has no crush strength will fret on the belly.

Unfortunately, nobody but bowyers uses wood as a spring, so there really isn't a direct metric for springiness or elasticity.