A Web Widget is essentially a piece of code which may be used on a web page without alteration being required. The most common widgets are advertising banners such as the Amazon banner below but may also be other content such as music, video, interactive games (see the end of this post for a game widget) or many other content forms.
Widgets have various names including badges and gadgets and may be specific to specific portals such as Facebook, Myspace, WordPress and YouTube. This website (organicweb.com.au) has been created using the WordPress content management system and the various items in the right sidebar are all widgets.
Advantages for Content Publishers and Organizations
The advantages for organizations distributing widgets is that they create links to their website and have the opportunity of communicating information which they require to be distributed (and the message may be adapted at any time due to the publisher/organization controlling the content). The widget below for example is distributed by the FBI and includes the top 10 most wanted criminals in the U.S.A.
Per the widget below, widgets come in many forms:
Widgets may also be personalised. For example, per the widget from Jango below, the author of this post is able to share his Jukebox (click on a picture in the widget and crank up the volume to play music) :
P.S. If this page has taken ages to load then you have just discovered one of the disadvantages of widgets; they slow page load times!