APKMirror is an unofficial app from the application download website APKMirror that lets you conveniently download tons of APKs. The app is basically a webview of the official page, so it doesn't really add a lot of new features, aside from a few visual customization options.
APKMirror is an interesting app for users who regularly visit the website for downloading APKs. It's not that if offers extra features or improved downloading speed, but at least it means having the service at the tip of your fingers, only a tap away at all times. Plus, the option of using the dark theme is a nice added bonus.