Xiaomi is following in the footsteps of many OEMs and releasing its apps onto the Play Store for faster updates, which avoids the long waits of firmware upgrades. However, Xiaomi is doing something differently: it's allowing users of other brands' devices to use its apps. After the capable Mi Calculator, now we have Mi FileExplorer on the Play Store. The app is still marked as "Unreleased" so it's still in beta, but from my tests it seems to work quite well.
Mi FileExplorer reminds me of the built-in file browser I've seen on my Samsung and LG devices: there's a regular directory browser, but also a per-type categorization that lets you view all your stored images or videos or APKs or documents (and other types) regardless of which folder they're in. And like all file explorers, there's a search function and all the expected actions like renaming, moving, copying, deleting, sharing, and so on.
However, Mi FileExplorer has a couple of bonus features that you may not find in your run-of-the-mill browser. First, there's zip/rar archive support for compressing or decompressing. Then there's a built-in cleaner for ridding your phone's storage of cache files. And finally there are a couple of options for wirelessly sharing files: Mi Drop for nearby devices, and an FTP server that lets you browse your device's storage from a nearby computer. It might not be as full-featured as Airdroid but it'd do the job in a pinch.
You can grab Mi FileExplorer from the Play Store for free and give it a go to see how it compares to your existing (or inexistent) file explorer. It should technically be compatible with many brands and devices, not just Xiaomi's. It's showing as compatible with my S7 Edge, my Galaxy Tab S2, and my Nexus 5X, but not with my Nexus 7 (2013) tablet. If you want to try it on an incompatible device or if you'd rather go the alternate download road, we've also got it on APK Mirror.