At a high level, there are 3 types of EC2 instances

• On Demand Instances (most common)
• Reserved Instances
• Spot Instances (this article)

Simply put, a spot instance is an EC2 instances that comes online when needed, based on usage or capacity. For example, let's say you have a web application that has periodic spikes in volume. Perhaps on the first day of the month, there is a signfiicant spike in requests. This is a great use case for spot instances, to add EC2 instances to your fleet during the spike.

To get started, in the left panel of the EC2 console, select Spot Requests > Request Spot Instances and then complete the form to specify the number of EC2 spot instances you would like to request.