My 2001 Corolla (4 speed automatic) manual states:
D: Normal Driving (Overdrive on)
2: Stronger engine braking (Overdrive off)
L: Maximum engine braking (Overdrive off)
Normal Driving: Use for normal cruising, hill climbing, hard towing, etc.
Engine braking: Turn off overdrive, shift into "2" when vehicle speed drops to or lower than 61mph. Shift to "L" when speed drops to or is less than 29mph.
CAUTION: NEVER put your foot on the gas pedal while shifting.
I hope you found this helpful. Engine braking is useful when you're going downhill-- this is better for controlling your speed on steep downhills (don't "ride your brakes", i.e. applying the brakes with slight or moderate forcer in order to slow down for the entire trip down)