A kernel is like the core of an operating system and everything else is built on top of it. When Android was created Google didn't want to create their own kernel from scratch they wanted to worry about more interesting parts for a mobile phone. So instead they took Linux which already existed It already been around for about 15 years by then and was already battle tested  and they built around it. There's a lot of different kernels out there but Linux has just become really dominant in terms because it works well, he says.