I wonder what is the difference between these two codes:

<label for='theinput'>Input here : </label>
<input type='text' name='theinput' id='theinput'></input>

and

<label>Input here : </label>
<input type='text' name='theinput' id='theinput'></input>

I'm sure it does something when you use a special javascript library, but apart from that, does it validate the HTML or required for some other reason?