This isn't the only reference to learn EJB 3.0 Look in the JBoss EJB 3.0 tutorial for loads of example programs and detailed text describing each example.
In some of the example listings, what is meant to be displayed on one line does not fit inside the available page width. These lines have been broken up. A '\' at the end of a line means that a break has been introduced to fit in the page, with the following lines indented. So:
Let's pretend to have an extremely \ long line that \ does not fit This one is short
Let's pretend to have an extremely long line that does not fit This one is short