What is the purpose of idling? Where is the idle speed? What effect does the tightness of the idle speed adjusting screw have on the car? thank you

Idle state refers to the working state when the engine is idling. The purpose of idle speed adjustment is to ensure the stability of engine idle speed. Too high or too low speed will have a negative impact on normal use. Excessive idle speed will increase fuel consumption and make shifting difficult. Too low idle speed will cause difficulties in starting, easy flameout, poor oil lubrication and increased wear.