Introduction
Laymen explanation
Are you a businessman who wants to create your own e-shop and you are thinking how to do this. Managing IT is not your core strength. Still, you need to take care of IT infrastructure, You might tell that I will use cloud infra instead of physical infra. Are you thinking that you are saved? Note that you still need to take care of VMs, infra softwares (JVM, OS) upgrade etc. Still you think so? Really not. Indeed there is potential saviour known as server less technology.
Technical explanation
Reference