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addEventListener is a method available on the EventTarget interface in web browsers, allowing developers to execute code in response to user interactions or other events. It is the standard way to attach event handlers to HTML elements, the document, or window objects. The method takes two primary arguments: the type of event to listen for, specified as a string (e.g., 'click', 'mouseover', 'keydown'), and the function to be executed when the event occurs, known as the event handler or listener.

A third, optional argument, `options`, can be provided to specify certain behaviors. This `options` object can include properties like `capture`, a boolean that determines whether the listener should be invoked during the capturing phase or the bubbling phase of event propagation. It can also include `once`, a boolean that, if true, causes the listener to be automatically removed after it has been invoked a single time. Another option is `passive`, a boolean that, if true, indicates that the listener will never call preventDefault(). This can improve performance as the browser doesn't need to wait for the listener's execution to know if the default action should be prevented.

addEventListener is preferred over older methods like `element.onclick` because it allows multiple listeners to be attached to the same event on a single element, and it offers more control over event handling, particularly with the `options` parameter. To remove an event listener, the removeEventListener method is used, which requires the same event type and handler function as were used when adding the listener.