FaaS

FaaS stands for "functions as a service."

The way that computers have worked in the past as that they are constantly running, waiting to be asked to do something.

FaaS, however, allows your code to sit at rest until it is asked for. When your application architecture requires that that piece of code be ran, that code will fire up, respond to the event that it needs to do its work for, and then go right back to sleep.

There are many implications to this but the main reason that they have become commonly used is that they are cheaper. Because your code doesn't always have to run, you don't have to pay for it to run and, effectively, do nothing. Instead, that computer can only run when it needs to be.

For more information, see Functions as a Service.