MIUI, or Mobile Internet User Interface, is a software developed by Chinese company Xiaomi to enhance the user interface of the Android operating system on their devices. While the "Pure" Android system does not include a dedicated UI theme, many other smartphone brands such as Samsung, OPPO, Coolpad, and Asus have their own UI themes that are specifically designed to improve the user experience and make it easier for customers to interact with their devices.

One way to see the original version of Android without any customizations is to look for AndroidOne devices, which are manufactured by several different vendors and are known for being affordable.

When compared to other Android customizations such as Samsung's TouchWiz theme, the MIUI experience may feel different as it has its own distinct design and appearance. This is because each manufacturer puts their own "touch" on the operating system they use.

MIUI is built using Java, C and C++ programming languages and uses a monolithic kernel, which is a modified version of the Linux kernel. The software is licensed under the GNU General Public License v3 and the Apache 2.0 license. The source code of the entire system is open-source, which makes it possible for any developer to access it and make any changes they see fit.

One of the great features of MIUI is its aesthetics, by providing a wide range of themes that users can choose to personalize the look of their devices. Also, MIUI comes with many additional features that are not present on stock android, such as dual apps, second space, and several privacy features.

One of the most notable features of MIUI is its built-in theme editor, which allows users to customize the look of their devices by creating their own themes. This feature allows even novice users to create professional-looking themes, which can be shared with other users as well.

Another feature that sets MIUI apart from other custom Android versions is the level of customization it offers. Users can personalize almost every aspect of the operating system, from the home screen to the lock screen, to the notification bar, and more. Additionally, MIUI provides a large number of built-in apps, that are designed to make your daily life easier such as, Mi Calculator, Mi Notes, Mi Remote, and many more.

Overall, MIUI is a great choice for users who want more control over their device's look and feel, as well as those who want to take advantage of additional features that are not typically found in stock Android. It is also an open-source, which means that anyone can make changes to it, this makes it a great choice for developers and power-users as well.