OEM producing the smartphone
Classification based on what functionalities are offered by the phone
Classification of smartphone according to basic shape
Operating system powering the entire smartphone. In an Android phone this is the OEM's fork on android with their customisations and features. Some of the most popular Android Skins include MIUI, Oxygen OS, Grace UI, HYC sense etc.
physical dimensions of the smartphone
Availability of various colors
Materials that constitute the body and structure of the smartphone