The prompt() method in JavaScript is used to display a dialog box that prompts the user for input. It is often used if the user wants to input a value before entering a page. The prompt() method returns the input value if the user clicks "OK", otherwise it returns null. The method takes two arguments: the first argument is the text to display in the dialog box, and the second argument is the default input text. If the user clicks "OK", the input value is returned. Otherwise, null is returned. The prompt() method can be used to take input from the user before proceeding with a task. However, it should be used sparingly as it prevents the user from accessing other parts of the page until the box is closed.