"A constructor is a method that will run when you instantiate the class."

A constructor is the main attributes of the object that creates an object from the template. Look at a class as a play-dough mold, and the variables it takes in is the play-dough, creating an object (the instance). Without the constructor, instances cant be made. The class itself is not an object, but a blueprint on making that object. the instances are the objects. So in other classes, i can make as many playdough molds as i please and use them separately as seperate objects of the same class, because of the constructor.

public class PlayDoughStar {

private String starColor;

public PlayDoughStar(String starColor) {
     this.starColor= starColor;
} 
//the rest of the class code
}

so in a different class, i want to make a play-dough star:

public class Table {
PlayDoughStar redStar = new PlaydoughStar("red");
PlayDoughStar blueStar = new PlaydoughStar("blue");
//Tables constructor here {
//}

The constructor is a method. It runs when you create a class instance. It has no return type. The name must be the same as a class name.

If you still don't understand what is it just tell me. I'll try to explain it in other words.

Have a nice day!

What does he mean by saying instance