HTML Form submit buttons

Answer 1

You should pass the <input type="submit">'s value attribute.

For example, if the user clicks the following submit button, the browser must send GoNext=Next+Step

<input type="submit" name="GoNext" value="Next Step" />

For more information, read the specification

Answer 2

You could pass any value and you can check based on various possibilities whether form was submitted. For example, this is how we check in php whether or not form was submitted:

<input type="submit" name="submit" value="whatever" />

if (isset($_POST['submit']))
{
  // form was submitted !!
}