You may have many apps on your device. You may also maintain groups on your device for those apps. When you want to open an app, you have to travel till that app and click on it. If you have 5 screens on the home and if your app is on the 5th screen, you have to navigate to the 5th screen and open the app.
Search app will be single point to search and open any app on your device.
Just type few letters of your app name in the search field and your app will be filtered. Just tap on it, your app will be opened.