In the past, the word 'gadget' has almost always applied to a physical object that you could use for some unique purpose. Gadgets could be useful to the point of saving massive amounts of time and energy for their users, or they could be little more interesting trinkets. Gadgets are almost always novel in some way or another though.
Now the word gadget has transcended the need to be a material object and also applies to some types of computer programs. Specifically Gadgets are now types of programs that are designed to be run on Microsoft's new Windows Vista operating system and to be run embedded in a special web based service offered by Microsoft. Because these gadgets come in two different varieties, those varieties are specified by the names of the gadgets. For example, Web Gadgets are embedded in the web page in a similar way to traditional applets. The Sidebar Gadgets are run in a special sidebar in the Windows Vista operating system.
These software Gadgets are available for download from a web site associated with Microsoft and perform a wide variety of functions. Web Gadgets can include programs that provide you with daily quotes, words of wisdom, games like hangman that you can embed in web pages, a clock displaying Greenwich Meridian Time, and software that can stream live video from web cams in various parts of the world (Europe seems to be especially popular). There are also HTML sandboxes and links to email that you can embed in a web page. One useful application that you can download and place in a web page is a text message window which will allow you and another person to communicate in real time from various websites.
The Sidebar Gadgets are also very impressive and can be downloaded and installed on your Vista operating system with a minimum of trouble. Examples of these programs include ones that rely on the web for information. You can get live news feeds, your local weather (or presumably someone else's local weather if you like), and information about ongoing eBay auctions. There's also one that lets you search various eBay sites right from your sidebar. Another Gadget will play music on your media player in a random order while displaying the art from the cover of the album being played. One Sidebar Gadget will also monitor your computer system's use of memory, as well as hard drive space used, and the use of the processor. If you happen to be Muslim, you can get a sidebar Gadget that reminds you when to pray. There's also one that will access your Microsoft Outlook calendar and remind you of your appointments.
Another great thing about Microsoft taking the initiative with these Gadgets is that they build a sense of community by encouraging people to create and submit Gadgets of their own. That means that you do not have to be part of some big software company in order to contribute the programs that are available for use by users of Windows Vista.