Widget

In computing, a web widget is a software widget for the web. It's a small application with limited functionality that can be installed and executed within a web page by an end user. A widget has the role of a transient or auxiliary application, meaning that it just occupies a portion of a webpage and does something useful with information fetched from other websites and displayed in place. Other terms used to describe web widgets include: portlet, web part, gadget, badge, module, snippet and flake.    

A widget is a stand-alone application that can be embedded into third party sites by any user on a page where they have rights of authorship, e.g. a webpage, blog,[1] or profile on a social media site. Widgets allow users to turn personal content into dynamic web apps that can be shared on websites where the code can be installed. For example, a "Weather Report Widget" could allow anyone to report today's weather by accessing data from the Weather Channel, it could even be sponsored by the Weather Channel. For website visitors to view, it must be embedded in a webpage, such as a Blogger blog sidebar. Even the portion of a blog where the ads are displayed is a widget.

Widgets were also added to the Windows Operating System. They first appeared in Windows Vista.[2] The default widgets include clock, CPU meter, picture puzzle and image slideshow. In 2012 Microsoft advised widget users to disable these from their PCs out of security concerns.[2]

Web developers have used third party code chunks in pages. Early web widgets provided functions such as link counters and advertising banners.

Widgets may be considered as downloadable applications which look and act like traditional apps but are implemented using web technologies including JavaScript, Flash, HTML and CSS. Widgets use and depend on web APIs exposed either by the browser or by a widget engine such as Akamai, Clearspring, KickApps, MassPublisher, NewsGator, Widgetbox or many others.

Definition from the Wikipedia website