Amazon EC2 Auto Scaling allows you to scale horizontally, therefore launching and terminating instances dynamically, based on your workload and the health of your application (responding to EC2 StatusChecks, ELB Health Checks, CloudWatch metrics...), but also with a schedule.

You create one or more instances in a collection which is called Auto Scaling Group.

You specify the minimum number of instances, the maximum and the desired capacity and EC2 Autoscaling will ensure that your group will have instances satisfying those ranges.

More about it here

auto scaling

Scaling can occur based on demand (performance) or on a schedule.

EC2 autoscaling provides Scalability and Elasticity, because not only it scales out, but it also in, reducing the number of instances when they are not necessary anymore.