id in div html code example

Example 1: html id

<p id="newid">this is the id</p>

<style>
#newid {
  background-color: green;
  text-align: center;
}
</style>

Example 2: referance html id css

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