What is 'for' used for in bootstrap form label?

Question

I don't know the meaning of for="inputEmail3", seems its same as id, what is it for? Can I just remove for="inputEmail3" ?

<form>
  <div class="form-group row">
    <label for="inputEmail3" class="col-sm-2 form-control-label">Email</label>
    <div class="col-sm-10">
      <input type="email" class="form-control" id="inputEmail3" placeholder="Email">
    </div>
  </div>

Answer 1

If you click on the label with your mouse, then the cursor will automagically jump to the input specified in the 'for' attribute. It's really useful, don't remove it.

Answer 2

for specifies the element id to which the label belongs.