Print this article for free. If a checkbox is checked, you can uncheck it. If it's unchecked, you can check it.
Radio buttons are different.
Once a radio button is on, it stays on until another one is selected. Then the first one goes off. Light off Light on This example looks very much like the checkbox example. This is pretty much just like the checkbox example earlier. There are a few more details about checkboxes and radio buttons, but those can wait until the next set of tutorials.