What, exactly, is set (like you were describing it to your grandmother 
)?
set is when an unstrung bow is unable to return to his original shape because of overstressed sections of wood usually resulting in compressed wood cells (crysalis) on the belly area
it's a consequence of bad tillering and/or asking too much from your bow
it may also happen to a bow left strung for too long
Not correct. It is the deformation caused by taking the wood close to its elastic limit. That's it.
