i know what it's supposed to do but what are it's electric components for an AC motor?
Speed controllers for AC drives such as soft starters or VFD. Utilize whats referred to as pulse width modulation. PWM for short.
Here is a starting place for you. Keep in mind their are different circuits that can generate PWM.
As for what are the components - that depends on how detailed of a list you want- the quick summary I would categorize by the specific engineering efforts:
System Control ( HMI or other "higher" level interface)
Real Time Control ( PWM Generation)
Drivers - Sensors and Isolation
Power Section ( DC Link, Switches typically MOSFET or IGBT, Cooling)
Filtering ( Basically trying to remove the PWM pulses to output an ideal sine to the motor)
Separate names with a comma.