opening screen; initial screen; start screen
Computing term for the first screen displayed when launching an application, game, or system.
When you launch the app, the opening screen is displayed.
トップ画面 is a more general term for the top or main screen of a website or app, while 初期画面 specifically refers to the very first screen shown at startup.
スタート画面 is often used for the start screen of an operating system or game, similar to 初期画面 but with a slightly more casual, user-facing nuance.
Compound of 初期 (しょき, 'initial period') and 画面 (がめん, 'screen').