Xiaomi is a relative new kid on the block when it comes to smartphones, launching its first in just 2011. The Chinese manufacturer has since seen a meteoric rise to success that puts it currently as the world's number 3 smartphone vendor by volume. In context, that puts Xiaomi behind only Apple and Samsung at the time of writing. Xiaomi's main success comes from its native China, and while its devices are not readily available globally, that is beginning to change. One recent big addition is that of India.
Away from smartphones, Xiaomi makes apps, smart TVs, a fitness band and a host of other products. But the thing it's probably most well known for away from actual phones is the software that runs on them. MIUI predates the first Xiaomi smartphones and is a complete re-working of Android as we know it. It's also available readily for non-Xiaomi smartphones.
Perhaps the most famous employee at the Chinese manufacturer is Hugo Barra, formerly of Google. Barra was formerly a high-up on the Android team but left to take up a position as Global VP at Xiaomi.