In general, serverless refers to an economical model where we pay for compute resources used as opposed to “servers”.
Wait… isn’t that what the Cloud is about?
Well, yes, on a macro-scale it is, but serverless brings it to a micro-scale.
In the cloud we can provision a VM, for example, run it for 3 hours and pay for 3 hours. But we can’t pay for 5 seconds of compute on a VM because it won’t have time to boot.
A lot of compute services have a “server-full” model. In Azure, for instance, a Web App comes in number of instances. Each instance has a VM associated to it. We do not manage that VM but we pay for its compute regardless of the number of requests it processes.
In a serverless model, we pay for micro-transactions.
This is the first part in a series and is aimed at giving a conceptual explanation.