Check out example codes for "nth-child() css". It will help you in understanding the concepts better.

Code Example 1

/*Specify a background color for every <p> element that is the 
second child of its parent:*/
 		background: red;

Code Example 2

tr:nth-child(even) {background: #CCC}
tr:nth-child(odd) {background: #FFF}

Code Example 3

/* Selects the second <li> element in a list */
li:nth-child(2) { 
  color: lime;

/* Selects every fourth element
   among any group of siblings */
:nth-child(4n) {
  color: lime;

Code Example 4

:nth-child(3) { //the number is the child number you are targeting
	//styles here 

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