为什么小白学编程到赋值运算符就觉得好吃力？

public class HelloWorld{
    public static void main(String[] args) {
    int one = 10 ;
        int two = 20 ;
        int three = 0 ;
        three = one + two;//three = 10 + 20;所以three的赋值变成30
        System.out.println("three = one + two ==> " + three);//这里的+three是什么意思？
        three += one ;
        System.out.println("three += one ==> " + three);
        three -= one ;
        System.out.println("three -= ==> " + three);
        three *= one ;
        System.out.println("three *= ==> " + three);
        three /= one ;
        System.out.println("three /= one ==>" + three)
        three %= one ;
        System.out.println("three %= one ==> " +three);
       
       
       
       
       
   
}
}

希望大神能详细解释下