Xiaomi is a privately owned company that designs and sells smartphones, consumer electronics, and accessories with its Android-based MIUI operating system. The document reviews several Xiaomi smartphone models, detailing specifications such as dimensions, weight, display, internal memory, camera attributes, and available colors for models including the Mi 3, Mi 4, Mi 4s, Mi 4i, and Mi 5. The overall focus is on the technical features and market presence of these smartphones.