Xiaomi GetApps is the official app store from Xiaomi where you can download hundreds of apps for Android. The app works perfectly on every device with an Android operating system, but you have to have the Xiaomi mobile services app installed in order for it to work correctly. Basically, the app probably won't work well on Samsung or Huawei devices.
Once you've logged into your user account, you can take a look at the various categories included on Xiaomi GetApps, such as communication, photography, video games, finance, and more. Under each category, you'll find a wide selection of apps ranked according to popularity.
Each app has a page with screenshots, general information on its features, the approximate number of downloads, and a link where you can download it yourself. The link also shows you how big the file is so you can make sure it's worth the space it takes up on your smartphone.
Xiaomi GetApps is an interesting alternative to similar app stores. It offers a wide range of apps and games for Android.