To understand the relationship of these attributes, it is easiest to think of a variable as a box with a label attached to the outside.
要理解这三个属性之间的关系，可以把变量简单的想象成一个外面贴着标签的盒子。
2
The name of the variable appears on the label and is used to tell the different boxes apart.
变量的名字出现在标签上用来区分不同的盒子。
3
The convert function takes the variable containing the input string, as well as a reference to the Label widget as parameters, so that it can change the value shown by the Label.