In computer programming, a widget (or control) is an interface element that a computer user interacts with, such as a window or a text box. Widgets are sometimes qualified as virtual to distinguish them from their physical counterparts, e.g. virtual buttons that can be clicked with a mouse cursor, vs. physical buttons that can be pressed with a finger. Widgets are often packaged together in widget toolkits. It is becoming common practice for programmers use widgets to build graphical user interfaces (GUIs). (Source- Wikipedia)
A widget (also known as a gadget) is a small program that runs on your desktop or web page all the time, which replaces the need to constantly visit a website in order to get common information. (source 2007: live.pirillo.com/)
Need more? In Laymans terms, this is about the best definition I could find.
Here’s what Wikipedia has to say about web page widgets:
Embeddable chunks of code have existed since the start of the World Wide Web. Web developers have long sought and used third party code chunks in their pages. It could be said that the original web widgets were the link counters and advertising banners that grew up alongside the early web. Later, ad and affiliate networks used code widgets for distribution purposes.
A widget is anything that can be embedded within a page of HTML, i.e. a web page. A widget adds some content to that page that is not static. Generally widgets are third party originated, though they can be home made. Widgets are also known as modules, snippets, and plug-ins. Widgets can be written in HTML, but also in JavaScript, flash and other scripting languages that will be run when the page is called.
Rich media, Interactive Entertainment widgets were first syndicated in large volume in 2001 by Miniclip. Widgets are now commonplace and are used by bloggers, social network users, auction sites and owners of personal web sites. They exist on home page sites such as iGoogle, Netvibes, Pageflakes, SpringWidgets and yourminis. Widgets are used as a distribution method by ad networks such as Google’s AdSense, by media sites such as Flickr, by video sites such as YouTube and by hundreds of other organizations.
Applications can be integrated within a third party website by the placement of a small snippet of code. This is becoming a distribution or marketing channel for many companies. The code brings in ‘live’ content – advertisements, links, images – from a third party site without the web site owner having to update.