Описание тега event-binding
Event binding connects an event handler to a specific event.
Event binding is the process of connecting (binding) an event-handler to an event listener.
The event handler is usually inline code or a function call, and is executed when an event happens to an object listening for the event.
In this code:
<button onclick="handleClick();">
onclick is the event listener and handleClick() is the event handler. The code binds handleClick to a click event on the button.