Clicking on a button will activate the action. Buttons can also be used to signal the users choice. It may restrict the type of text the user can enter, i.e. numeric. Sometimes referred to as a Radio Button, an option button is used to select one of two or more mutually exclusive options. Click on an option no selected will deselect the previous on and select the one clicked on.
Option buttons are usually round to differentiate between option buttons and check boxes.
Check boxes are not mutually exclusive, and it is possible to select more than one. Check boxes will usually be square to differentiate between check boxes and option buttons. Toggle buttons differ from regular buttons in that when clicked, the button will stay 'down' to signify the 'On' position. Clicking it again will put it in the up or 'Off' position. A 'close relative' of the toggle button is the multi-state button.