All the realistic free fermionic models utilize a set of basis vectors, the
NAHE set, that correspond to Z2×Z2 orbifold compactification with
nontrivial background fields. I argue that the realistic features of free
fermionic models, like the number of generations and the fermion mass spectrum
are due to the underlying Z2×Z2 orbifold compactification.Comment: 4 pages, latex, To appear in proceedings of the Beyond the Standard
Model IV Conference, Lake Tahoe, CA, Dec 13-18, 1994. IASSNS preprint number
is corrected