What does "forced car mission" mean?

Hi.

What does "forced car mission" mean? And what does the command "SetForcedCar ()" mean?
Maybe it means when the car doesn't break, but I'm not sure.
I tried and nothing changed the tasks. I'm sorry, I'm still very beginner.

Thanks the answers.

Forced vehicle/"forced car" missions are missions in which the player is forced to use a specific vehicle during the mission (such as Level 2-Mission 5: Better Than Beef, which forces use of the Pickup Truck). Usually, there will be a timer if the player exits/destroys the vehicle which fails the mission if it runs out and some other minor precautions during these missions. The command itself is what removes Phone Booths from the map/makes them unfunctional for the duration of the mission as far as I know.

Thank you.

I have a some more questions.
What do the following terms mean?

"SetNormalSteering"
"SetSlipSteering"
"SetSlipSteeringNoEBrake"
"SetSlipEffectNoEBrake"

"SetCMOffsetX(0.0)"
"SetCMOffsetY(0.2)"
"SetCMOffsetZ(0.2)"

"SetBurnoutRange(0.2)"
"SetMaxSpeedBurstTime(2.0)"
"SetDonutTorque(5.0)"

Thank you very much.