[CL8]

One of the emergency maneuvers I have our drive students perform is having the car "stall" in the middle of a turn.
I take them to a quite road or large parking lot, have them start into a turn at normal speed (about 10mph right turn, 15mph left turn) as they start the turn, I turn the key to shut off the engine. they are to continue to turn until almost straight (to see how it feels to steer with no power steering) then push the gear in neutral, restart, pull it back in drive and lightly step on the gas.
Recently one of my students stepped on the gas, very hard, in neutral before he put it back in drive. We did the maneuver a second time and he did the same thing. The Check engine light came on immediately as he pushed the accelerator in neutral the second time.
I know doing that triggered the light, I told him not to worry about it, we ended the lesson about a half hour later, I figured the light would go off before the lesson ended, it didn't go off until 2 days later.

The vehicle is a Toyota Echo

My question is,
1.What exactly was happening in the engine when he did that, to set off the light?

In training I was told when the Check engine light comes on it means the computer senses too much pollutants coming from the exhaust system.
2. Is that correct, and is there a difference between the check engine light and the emissions warning light?
3. Why would the light have stayed on for two days after that?

Thanks for any input,
Cl8