The Password Input Element is the same as a text input except the echo print is all stars. This code gives you the following text box. Type in it to check out how it works. You would normally see the input item at this point, but hidden elements aren't visible. They are used to store data about the current page that is used by server-side programs.
Value is the actual string returned by the getParameter call described below.
If no value is specified, the string following the option is returned. In this case 7. They differ from radio buttons since more than one may be checked. When you use check boxes that all have the same name, you have to parse the string returned to look for commas. If you had given the check boxes below the same name, and check boxes 1 and 3 you would get 1,3 back as your results.