From C++ A Beginner’s Guide by Herbert Schildt Chapter8 page 34
The definition as below:
You can access an object either directly (as has been the case in all preceding examples), or by using a pointer to that object. To access a specific element of an object when using a pointer to the object, you must use the arrow operator: –>. It is formed by using the minus sign followed by a greater-than sign. To declare an object pointer, you use the same declaration syntax that you would use to declare a pointer for any other type of data. The next program creates a simple class called P_example, defines an object of that class called ob, and defines a pointer to an object of type P_example called p. It then illustrates how to access ob directly, and how to use a pointer to access it indirectly.
大概意思就是說當你使用了指針來操作一個對象的時候，你在要通過這個指針來訪問對象的成員，就不能再使用 dot operator '.'，必須使用 arrow operator '->'.
下面也是教程中的示例：
