The term widgets can refer to several different concepts in Android. When most people talk about widgets, they are referring to app widgets, which are typically seen on the home screen. App widgets are like mini applications by themselves as they usually provide a subset of functionality, based on their main application. (Usually, most app widgets are installed along with an application, but that is not a requirement. They can be standalone apps in a widget format.) A common app widget example is a weather application that offers several different app widgets for the home screen. Chapter 6, Beyond Your App - Home Screen Widgets, Search, and the System UI, will discuss home screen app widgets and provide recipes to create your own.
When developing for Android, the term widgets generally refers to specialized Views placed in the layout files, such as a Button,...