What is the first line of code in the example below

以下示例中的第一行代码是什么

<p><p a>

I saw a youtuber writing the below code and it displayed a design in cssbattle challenge.I also tried it,it works.But I never saw it on any HTML tutorials before and I searched it on Google but it was showing resuts for paragraphs tags only which I already know.here is the link for the youtube video.

我看到一个youtube用户写下面的代码，它显示在cssbattle挑战的设计。我也试过，它的作品。但我从来没有见过它在任何HTML教程之前，我在谷歌上搜索它，但它只显示段落标签的结果，我已经know.here是youtube视频的链接。

<p><p a>
<style>
  body{
    background:#E6D9AC;
  }
  p{
    width:91px;
    height:30px;
    padding:30px 0;
    border:30px solid #BD6C27;
    border-right:none;
    background:#BD6C27;
    position:absolute;
    top:44;
    left:125;
    background-clip:content-box;
  }
  [a]{
    background:#8F2D2B;
    border-color:#8F2D2B;
    left:155px;
    top:74px;
    rotate:-180deg;
    background-clip:content-box;
  }
</style>

I know about <p></p> tags but this <p><p a> tag, I didn't see it in HTML before. Do you know what it is called?

我知道

标记，我以前在HTML中没有见过。你知道它叫什么吗？

<p> is opening of a paragraph tag/element. <p a> is just another opening of paragraph tag/element with an attribute a. As you can see from the video, person selects elements with attribute a using [a]. It's used to just to differ paragraph elements. But this HTML is not valid since paragraph elements dont have a closing </p> tag.

是段落标记/元素的开头。

只是具有属性a的段落标记/元素的另一个开头。正如您从视频中看到的，Person使用[a]选择具有属性a的元素。它通常只是用来区分段落元素。但此HTML无效，因为段落元素没有结束