A complete HTML example document:
<input type="button" onClick="foo()">If you don't understand what the onClick event is, don't worry. We'll be getting to that later. You can also place it on the right side of a name/value pair. For example:
<input type="text" value="compute_value()">In this example, the value returned by the function compute_value is returned and is used for the value of the INPUT tag.