Stateless vs Stateful beans

Hi,

I am new to Java web development and I need a solid real world explanation of the difference between these two terms if anyone can help? I keep reading things like this for stateless session bean descriptions "...work can be performed within a single method invocation, or it may span multiple method invocations... in which case a stateful session bean would be required." I also read that stateless beans works with a single client. I know what a method is and how they work and a bean is a java class, but in this context ("method invocation") I am a bit confused.

Also, can anyone recommend a good book on EJBs? I was looking at the Head First EJB book but its almost ten years old at this stage.

Thanks in advance.