What is Soc in smartphone or tablet. Why is it use for?

Reading specifications and features of a mobile phone on a technology website is making me confuse regarding a single specifications which i am unable to understand. Can anyone tell me that what is the meaning of Soc in smartphone and tablet and also why is it use for?

Hi, SOC in an Android phone means a System On Chip. Where all the things such as ic's are joined at a single chip so, that if some thing can not be broken in chip.
It works as a single entity and not as different-different parts.