difference in Data Binding Statements?

Hey all, what is the difference between DataBinder.Eval and Container.DataItem? I have noticed that when I use the Container.DataItem("Field Name") it works, but when using the Microsoft VS.NET DataBinding utility (clicking on the DataBind... property), it wants to write out DataBinder.Eval(Container, "Field Name"). How do these two differ and why does 1 work while the other doesnt?

Thanks,
-md