Nutrient is usually just vitamins/minerals
Energizer is usually DAP, a nitrogen source, and sometimes they add yeast hulls to the mix.
for making mead you want both. I've done good mead with staggered additions of Nutrient and energizer vs. goFerm and Fermaid K
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10