A web widget is defined as "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, or profile on a social media site."
With regard to Episerver Personalization, a widget is a block of recommendations. A widget can display any number of recommendations but a 'widget' will refer to that particular block. You can have any number of widgets per web page.
Please see the example of a simple widget below on our Quicksilver reference store. The widget is highlighted in the red box. This is a product page displaying one widget with 10 recommendations.
Once a widget is enabled and configured in the Personalization system, clients will be sent through information for the product(s) Episerver Personalization has chosen to recommend and then the client will use this information to build and display the the widget on the front-end of the site. This gives the client full control of how recommendations look on the site.