"Elastic resources are applications and infrastructure that can be summoned on demand when traffic or workloads get high. Cloud computing businesses such as AWS and Google Cloud rely on elastic resources as a business model to bill customers on-demand like a utility bill. This supply side and demand side economic cycle are the underpinnings of the cloud ecosystem. A good example of an elastic resource is an EC2 server. If a business only requires 2 servers to run their website, but see a holiday traffic spike, they can simply allocate additional elastic resources by increasing the EC2 servers from 2 to 4 to handle the holiday traffic load. Once that traffic dies down, they can deprovision the servers back to 2. This is an elastic resource."
in other words
Sweatpants for your apps.