Check out example codes for "how to call an id in css". It will help you in understanding the concepts better.
Code Example 1
/*put a # infront of the id*/
/*<section id="example"></section>*/
#example{
margin: auto;
}
Code Example 2
<style>
#selector {
color: red;
}
/* # is id selector */
</style>
<div id="selector">
<p>This is an id</p>
</div>
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