A static page is a document; an interactive page is an application. Event binding is the mechanism that turns your templates into living interfaces.
1The Callback Pattern
Event binding creates a 'reaction' to a user action. When an event occurs (like a click, a hover, or a keystroke), Angular executes the expression you provided. Usually, this expression is a call to a method in your component class. This keeps your template clean and moves the complex logic where it belongs: in your TypeScript code.
2The $event Payload
Sometimes simply knowing that an event happened isn't enough. You might need to know which key was pressed or the current value of an input field. Angular provides a reserved variable called $event that contains the standard DOM event object. By passing this into your method, you gain full access to the event's properties and the element that triggered it.
