Q:

What does this html mean?

Just wondering what the 'event' keyword means in this instance? Is it a keyword and passing the actual event that will contain the keycode?
<asp:TextBox ID="tbSearch" runat="server" onkeyup="return dontSubmit(event);">

    <script type="text/javascript">

    function dontSubmit(event) {

        console.log('dont submit');
        console.log(event.keyCode);

    }

</script>

A:

The event object is passed by the browser to event handlers when an event occurs in order so you can query different information about the event ( such as x/y position, key clicked, etc ). 
Note: It can be named anything, so if you change function(event) to function(lol) and reference it with lol it would work the same way.
See https://developer.mozilla.org/en/DOM/Event for more info.

