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

Code Example 1

p:first-of-type {
  font-size: 1.25em;
}

Code Example 2

p:first-child {
  background-color: yellow;
}

Code Example 3

:first-of-type {
	//styles here
}

:first-child {
	//styles here
}

:nth-child(1) { //the benefit of this is you can do it for 2nd, 3rd etc...
	//styles here 
}

Code Example 4

:first-child {
	//styles here
}

:nth-child(1) { //the benefit of this is you can do it for 2nd, 3rd etc...
	//styles here 
}

Code Example 5

p:first-child
 { 

   background-color: yellow;

 }

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