I've looked all around but simply can not find a detailed explanation on what the Mooncloth spec does exactly. Anyone care to share?

Mooncloth == +healing
Spellfire ==  +fire and arcane damage
Shadoweave == +shadow and frost damage

The difference is in what you make from the different cloth, not what the cloth itself does.  For instance, the Primal Mooncloth Set is healing gear...

Hope that helps!