"normal" 和 none 值在 CSS 属性 内容中有什么区别?

What's the difference between "normal" and " none " values in CSS property content?

我正在学习 css,但我不明白“内容”属性 的这两个值(正常值和 none)之间的区别。 这些值相同吗??如果是这样,为什么我需要两者?

<style>
  .p01::before {
    content: none;
  }
  
  .p02::before {
    content: normal;
  }
</style

来自the specification

normal

For ::before and ::after, this computes to none.