Just Out Of Curiosity...

If a shield has absolutely no DEF stat (i.e faerie shield) will it ever block? If it does block, will it reduce damage?

I have read this. What I mean is, if there is no DEF then that means there is no damage reduction (from what I have read). But does that mean that there is no damage reduction when I am hit without the shield blocking, or does that mean that when the shield blocks the same amount of damage will be dealt regardless of the block? And if it has no DEF will it even block in the first place?