Reading Type
Readings are any content you can dream up. These are the different types, which mostly specify how the content is to be accessed:
Plain text - the easiest type. You can just type (edit) the page into a form on the following page.
Reference - a scholarly reference to a journal or book.
Uploaded file - displays any file you have uploaded into the course. See the 'Files' section.
Web Link - A URL to somewhere on the web. When anyone clicks on this reading activity they will be taken out of the course (the page you've specified will fill the browser window).
Web page - A URL to somewhere on the web. Like the previous type, this will display a web page. Unlike the previous type, though, the page will displayed within a frame, as if it is integrated within the course.