i-vtec is variable valve timing PLUS VTEC????
VTEC means "Variable valve Timing and lift Electronic Control" and the i in i-VTEC mean intelligent.

A normal engine has to trade off performance between low rpm and high rpm. With VTEC ur engine is tuned for low rpm when running low and changes it behavior in the high rpms. The intelligent vtec just takes it one step further and "tunes" the engine more times than the regular vtec.