Only the timing (phase) of the valve events. It advances the timing (opens valves earlier) or retards it (opens valves later). What it doesn't change: Valve lift (how far they open) or duration (how long they stay open).

A smoother, more efficient engine across the RPM range. Most modern cars have some form of VVT (often called VCT, VANOS, VVT-i, etc.). It's standard, reliable, and great for daily driving. Act 3: VTEC (The Dual-Personality Cam) VTEC, invented by Honda, is a more dramatic and performance-oriented system. It's a mechanical trick inside the camshaft.

If your car has VVT, it's a smart, efficient daily driver. If your car has VTEC , it has a split personality—docile until you rev it out, then it turns into a race engine. And if it has i-VTEC , it has the best of both worlds.

That's an excellent question, and the short answer is They are often confused because they both manipulate engine valves and have three-letter acronyms, but they work on different principles to achieve different goals.