<head> and the
<body>. Depending on where we place it, the browser will handle it differently.
Waits to load the whole thing at beginning of page load
At the end of page load
To assign behavior to a specific event we say that we "register an event listener". An event listener is simply some code that specifies an event and a action to perform when that event happens. Once registered, the listener waits, or "listens", for the event to occur, and when it does, performs the defined action.
Unless otherwise specified, the event listener will continue listening for events and performing the defined actions. This can be tricky because one cannot predict how many times and event will occur and in what order a set of events might happen. This is one of the unique challeges of web development and event-based programming.