The immediate attribute if set to true can force validations, events and conversions processed during request phase of the lifecycle. Command component’s immediate attribute indicates what happens when the component gets activated. If the button’s immediate attribute is set to true and associated text field’s immediate attribute set to false then the event is processed without applying the field’s value to the model. In other words the value entered in the field does not even reach the model when the button is clicked but immediately processed in the above scenario.
The rendered attribute indicates whether a component should be rendered or not in the view page. Rendered attribute can use arithmetic operators and literals with rvalue expression but not lvalue expressions.