and beyond their return type, the represent two completely separate and distinct 'namespaces'.
If you submit a form, then the form elements are available through the getParameter() method. There is no corresponding setParameter().
If you place something with setAttribute(), it's available through getAttribute().
If you submit a form that contains a field named "foo", then trying to access the value through request.getAttribute("foo") will not work. Similarly, if you previously used setAttribute("foo2", "Hello"), you cannot get the String "Hello" back out by using getAttribute("foo2")
Attributes are variables used for sahring in an application. There are four "places" to store attributes. Request, Context, Session and pageContext(JSP). Parameters like Mike mentioned are with respect to HTTP requests.