What are JavaScript events?

JavaScript events are actions that occur in the browser — user interactions or browser-triggered occurrences — that JavaScript can respond to. Add event listeners: element.addEventListener("click", handler). Remove: element.removeEventListener("click", handler) (same reference required). The event handler receives an Event object with properties: event.target (element that triggered the event), event.currentTarget (element the listener is attached to), event.type, event.preventDefault() (prevent default browser action, e.g., form submit or link navigation), event.stopPropagation() (stop bubbling). Common events: click, input, change, submit, keydown, mouseover, load, DOMContentLoaded, scroll, resize. Use { once: true } option to auto-remove after first trigger.