Components let you split the UI into independent, reusable pieces, and think about each piece in isolation.
组件可以让你把UI拆分为独立的，可重复试用的碎片，并且对这些彼此独立的碎片进行思考。
Conceptually, components are like JavaScript functions. They accept arbitrary inputs (called "props") and return React elements describing what should appear on the screen.
概念上，组件很像JavaScript函数。他们接受任何输入（称为“props””）并且通过返回的React元素来描述将会有什么展示在屏幕上。
