The term home screen refers to the primary navigation screen for mobile devices, such as a smartphone or tablet. The home screen generally contains shortcuts to launch apps on the device or perform a search on the Internet. At the top of most home screens, there is a bar containing notifications and information about connectivity and battery life.
If you're familiar with computer's, you can think of the home screen as the desktop.
On the home screen, a user can arrange app icons in order and place them into groups with other similar apps. This action of grouping icons together makes it possible to have many more apps be accessible from the home screen. The home screen is usually accessed by pressing either a physical or touch home button at the bottom of the device. For instance, the circular button found on an iPhone or iPad, or on Android devices, the icon shaped like a house.