What are some ways to use AWS EC2?

You can use EC2 virtual processing engine for various aspects depending on your needs.
It can support different OS , different processing instance type and different size for your need. On top of it you can install software, run database servers, club them together as a web server cluster, Proxy server, IPS agent, IDS agent and the list keeps on going.

In simple terms you can imagine a EC2 instance a configurable cloud server engine.Configurations include size , memory , and the underlying storage EBS , instance store EFS etc.