Judie, All I know is that it used Google Chrome and Gmail. What is "under the hood" is something that I do not know. I paid $249 for it, gave it to a friend. I bought the person a wireless mouse, to make it easier to delete spam and junk mail.
Chromebook is Google Chrome operating system. It updates itself. While some apps work on Chrome and Android not all do, do they are different OS. No software to buy. Like a tablet with word process and spreadsheet and cloud computing all build in.