Check out example codes for "html id". It will help you in understanding the concepts better.

Code Example 1

<style>
  #test {
  /*Styleing here*/
  }
</style>
<h1 id="test"></h1>

Code Example 2

<style>
#grepperHeader {
  background-color: lightblue;
  color: navy;
  padding: 40px;
  text-align: center;
}
</style>

<h1 id="grepperHeader">grepperHeader</h1>

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