AMI, or Amazon Machine Image, is a powerful tool used in AWS that allows you to build a custom prepackaged image or use a prepackaged image provided by a 3rd party vendor or amazon that includes configuration, software, monitoring etc. An advantage of this is your system will have a faster boot time as this software is prepackaged and it saves you time as you can deploy several EC2 instances from 1 AMI so there is no need to download software manually on EC2 instances. You may be thinking, “Why not just use a user-data script on boot that installs this software?” You could do that however the boot time would be slower as the instances would boot and then install the software, but the AMI comes with it prepackaged. Your AMI is created within a specific region, but can be used across AZ in that region. If you wish to use your AMI in another region you can copy it. In order to create an AMI you first create the EC2 instances with the desired configuration, software, etc. Next you power off this instance to maintain data integrity and create the AMI from it, this will create EBS snapshots as well. Finally you can use that AMI to deploy future EC2 instances. It is a very powerful and useful tool!