What is the first screen in app?
Splash Screen is the very first screen the user sees when they open up an app on a mobile device. It's the very first chance of creating a positive impact on the users. It appears while the app is loading when the user has just opened up the app. Many times the Splash screen is called a launch screen.
Why do apps make you sign in?
The main reason services require you to sign in with a social network account is a security measure called OAuth. We've talked about OAuth before, and it's pretty simple: it's a means to log in to a third-party site (like the Gawker discussion system) using your Facebook, Google, or Twitter information.