https://www.cnet.com/news/want-fortnite-for-android-you-wont-get-it-from-the-google-play-store/

Epic Games confirmed on Friday that it plans to bypass Google's Play Store for the eagerly awaited Android launch of Fortnite, its galactically popular online shooter. Instead the developer will point visitors to its site to download and install the game. 

Installing an app from anywhere but the official app store is known as sideloading, and requires reducing the security on your phone by opening it up to unknown developers -- until or unless you remember to turn it off.