Specifically, do absorbs protect shields or do shields protect absorbs?
I take it you're referring to the Life absorb shield that lets you absorb 400 damage points with no injury?
Basically, the shields help lower the damage done to the absorbs so the absorbs last longer in attacks. The only thing the absorbs don't protect you from are the death spells that suck life out of you to pass back to the caster.
Specifically, do absorbs protect shields or do shields protect absorbs?
To answer your question, directly, It depends on which shield was cast first. Shields are used in REVERSE order of when they were cast. For instance, if you have a 400 absorb shield, cast, then a 50% tower shield, and your opponent cast a 500 damage spell, it will only do 250 damage to your absorb shield, and it will have 150 remaining damage to absorb.
If the Tower shield was cast first, and then the absorb shield, and you are attacked for 500 damage, your absorb shield will be destroyed, with 100 damage remaining, and that would be halved by your tower shield, and you will take 50 damage, and have neither the tower or absorb shield.