Boxes: Are usualy found in FORMS, where you can type into a text field, or check a checkbox, or pick from a dropdown box, or make a choice between some radio boxes.
The dropdown box will drop down to give you spcific choices, Like picking between red or blue background colors. To get the white background color again, press the Reload button up on the Tool bar.
You can select as many checkboxes at a time as you wish.
Usually you will be able to only select one radiobox at a time, if the page author changes this, they should imform you about how many radioboxes can be selected at any time.