Final answer:
An event handler is a method in programming that gets executed in response to an event, such as a mouse click or a key press, enabling interactive applications.
Step-by-step explanation:
A event handler is a special type of method that's executed when an event occurs. In programming, an event can be something like a mouse click, a key press, or a timer reaching zero. Event handlers are critical in creating interactive applications, as they allow the program to respond to user actions or other significant occurrences.
Often found in graphic user interfaces (GUIs), these methods are commonly written by programmers to perform specific tasks whenever the corresponding event is triggered.
For instance, a button in a user interface might have an event handler that contains the code to be executed when the button is clicked.