Cloud Computing is the on-demand delivery of IT resources over the Internet with pay-as-you-go pricing. Instead of buying, owning, and maintaining physical data centers and servers, you can access technology services, such as computing power, storage, and databases, on an as-needed basis from a cloud provider like Amazon Web Services (AWS).

What is EC2?

EC2 (Elastic Cloud Compute) allows you to launch as many or as few virtual servers as you need, configure security and networking, and manage storage. Amazon EC2 enables you to scale up or down to handle changes in requirements or spikes in popularity, reducing your need to forecast traffic.

Concepts and terms

The EC2 service can be broken down into the following components:

AMIs,

Instance types,

tenancy,

user data,

storage options

security,

instance purchasing options. 

https://dev.to/aws-builders/aws-ec2-elastic-compute-cloud-cheat-sheet-write-up-4lc5