According to the W3C, the onclick event is triggered by the keyboard for accessibility purposes:
SCR35: Making actions keyboard accessible by using the onclick event of anchors and buttons
In order to provide a better user experience for those without the use of a mouse, browsers have been developed to fire the onclick event even if the click occurs with a keyboard.
For this reason, jQuery’s click event will fire even if the checkbox is clicked by using the keyboard’s spacebar. change, obviously, will fire every time the checkbox’s state changes.
The checkbox just happens to be the special case where change and click are interchangable, because you can’t fire the change event without also triggering click.
Of course, the exception to this rule is if you were to use javascript to manually alter the checkbox, such as:
/* this would check the checkbox without firing either 'change' or 'click' */
$('#someCheckbox').prop('checked',true);
/* this would fire 'change', but not 'click'. Note, however, that this
does not change the checkbox, as 'change()' is only the function that
is fired when the checkbox changes, it is not the function that
does the changing */
$('#someCheckbox').trigger('change');
/* this would fire 'click', which by default change state of checkbox and automatically triggers 'change' */
$('#someCheckbox').trigger('click');
Here’s a demonstration of these different actions: http://jsfiddle.net/jackwanders/MPTxk/1/
Hope this helps.