Connection between function upon objects, constructors and extended objects

index.js

function Car(brand, model, seats, passengers) {
  this.brand = brand;
  this.model = model;
  this.seats = seats;
  this.passengers = passengers;
}

var bmw = new Car ("BMW", "X5", 5, 0);
var lexus = new Car ("Lexus", "L300", 4, 0);

Car.prototype.start = function () {
  console.log(this.brand + " start");
};

//bmw.start();

Car.prototype.embark = function (passengers) {
  if (passengers + this.passengers <= this.seats) {
    this.passengers = passengers;
  } else {
    console.log("Too many passengers!");
  }
}

Car.prototype.disembark = function (passengers) {
  if (passengers <= this.passengers) {
    this.passengers = this.passengers - passengers;
  } else {
    console.log("not enough passengers to disembark!");
  }
}

// bmw.__proto__ === Car.prototype; --> true
// lexus.__proto__ === Car.prototype;

//Extending the car prototype

function ECar (brand, model, seats, passengers, plug){
  Car.call(this, brand, model, seats, passengers)
  this.plug = plug
}

ECar.prototype = Object.create(Car.prototype); // connects .__proto__ from HybridCar to car.prototype
ECar.prototype.constructor = ECar;

const bmw2 = new ECar("BMW", "i3", 3, 0, "big blue one");