What is 'progressive shifting' in vehicle operation, and how does it benefit the driver?

1. Shifting gears at the lowest possible RPM that allows the engine to pull the next gear, optimizing fuel economy
2. Shifting gears strictly at the engine's maximum redline RPM to gain speed
3. Continuously shifting between neutral and drive while in traffic jams
4. Shifting gears without using the clutch by matching engine and vehicle speeds