What does it mean to change gears in a car?

I'm taking a Summer class at my university called Behavioral Analysis.

We have this term called a "behavioral antecedent" which basically is anything that signals you to perform a certain behavior such as a green light telling you to go or your mom's voice calling your name, signalling you to come to her.

This guy said that a behavioral antecedent would be when your "engine MPRs start to rise around 2500 to 3000, that's an antecedent for you to upshift."

Most of us didn't understand what that meant. This one girl said, "What are you talking about, the 2 and 1 on a gear shift is just there for towing, you're supposed to keep it in drive, numb nuts. This was never a thing."

That was quite rude, but I personally don't know why you would switch gears in a car. Why do you do this? I personally just keep my car in drive. I currently drive a 2007 Honda Civic.

The reference is not to automatic transmissions, which most cars have now.

The reference is to standard manual transmissions -- a stick-shift transmission. If you drive a stick, you have to start in 1st gear. At 10 mph you can push in the clutch and shift into 2nd gear. At 20 mph you can shift into 3rd gear. At 30 mph you can shift into 4th gear. At 40 mph you can shift into 5th gear and stay there.

For drivers who watch their tachometer, rather than their speedometer, they watch for engine RPMs (revolutions per minute). At 3,000 RPM, it's time to upshift again. The engine is working too hard in its current gear.

By the way, please ask people who are not well informed to refrain from calling people "numb nuts." You are right to ask for clarification.

Lol, he is talking about a manual transmission or otherwise called a "stick"… In a vehicle with a manual transmission you change gears constantly… You upshift as you accelerate and downshift as you slow down… This is about as simple as I can make it without explaining all of the details of how the gears work… The video below will help…
https://m.youtube.com/...hRwgRN3f1A

Most cars have the 2 & 1 but a "standard"
Aka a stick shift you have typically 5 gears that allow you the driver to shift instead of your engine doing it "automatically". 2500-3000 is an indicator in RPMs