On the whole serverless is basically any technology/service which allows you do things exceptionally cheaply or by paying the absolute minimum to what you’re using.
This is what makes serverless vs managed services. E.g. Postgres is not serverless, but on-demand Aruroa is because you pay for the RDS instances while they’re running “doing nothing” while the Aruora DB only is paid for while it’s used + storage costs.
S3 is in many ways “serverless” like that because you only pay for what you use, when you use it.
To be continued