Answer 1

The 'name' attribute is used as the name of the variable on server side. For eg.
<input type="text" name="username" />
<input type="password" name="password" />

on server side (let's say PHP) they become
either
$_GET['username']
$_GET['password']
or
$_POST['username']
$_POST['password']
depending on the "method" attribute of your form.
These variables are then used for various purposes which may include user authentication, registration, and many others.