A widget is an online tool and application that can perform any number of coded functions e.g. price check, weather, most popular stories, market data and so on.
Much like apps, widgets can be custom built for brands and are designed for sharing across the web and social platforms. Well-crafted widgets can be great way of gaining visibility, adding interest and getting a large volume of traffic to your site.
For a widget to be successful it has to bring something to the value of the site in which it is embedded.