VTEC = Variable valve Timming with Electronic lift Control

Some form of it or another has been used in Formula 1 racing for 20 years by various manufacturers, but Honda was the first to mass produce engines with variable timming. It was first introduced on the 1989 Acura NSX super exotic. Then in 1994, on a mass scale for affordable cars, on the Honda Prelude VTEC (think Si, but faster). By the late 1990's, everyone and their brother had gotten in to variable timming (BMW's VANOS, Toyota's VVT-i, etc). And even manufacturers of engines without it got into the whole accronym marketing thing (GM's ECOTEC, Ford's DURATEC, etc.).

It works by having twice the amount of cam lobes for each valve. One for normal operation at normal speeds. The other, when you hit the gas, a computer running the engine hydraulics, shifts the cams over to large lobes for longer duration, deeper opening, and faster operation. This ultimately alters the engine's timming which produces more power and essentially, a turbo effect (without the nasty spool up and such)

Original VTEC motors (like mine), were designed to engage at a set RPM (mine's at 4800). Today's i-VTEC motors (like the Acura RSX and TSX) are infinitely variable, so VTEC can engage at any RPM, proving even more instant response when you downshift and hit the gas.

Very good system.