Why is "for" used in HTML?

Question

I have seen in many places that in HTML forms the for is used I am unable to understand why?

I found this answer in Stackoverflow but was unable to understand it completely if possible can someone explain it in simple terms:-

https://stackoverflow.com/questions/12894169/what-is-the-html-for-attribute-in-label

Answer 1

For attribute is usually used to link the label tag with the input tag related to it

For example:
<label for='firstName'>First Name</label>
<input type='text' id='firstName'/>

Note that the for attribute value should be the same value we use for the input id that's how the browser know they are linked together.