4.1.1 has the following text
//The query parameters method is used in simple cases when default UserInfo and ID Token claims are desired and requests and responses do not need to be signed or encrypted. The request parameter method is used by sending a OpenID Request Object when a different set of UserInfo and ID Token claims are desired. The request parameter method also allows requests and responses to be signed or enrypted. Clients SHOULD use the request file method when passing the OpenID Request Object to minimize the request string. //
It should be separated into three paragraphs. More explanation on request file method should be added as well.