Use the website straight away
The phone browser gives you title search, the movie catalog, television pages and My List. You do not need an APK to browse. Use the menu button for the main links when the screen is narrow.
Shortcut or application?
A bookmark or home-screen shortcut opens the website. It does not install a native player or keep a copy of every movie. Use the shortcut option offered by your browser if you want a quicker return.
Looking at an app with the same name
This website does not distribute a native 123Chill APK. Other apps using the name can have separate developers and features. Check whether the app describes full-video viewing, trailers or movie information, rather than assuming the name tells you what it does.