AWS itself is a huge subject, but if your specifically looking at running SQL Server on AWS you really have two options:

1. RDS - A cut down version of SQL Server with limited functionality but the basics of HA \ DR covered

2. SQL Server on EC2, essentially SQL server running on a virtual machine hosted by Amazon.

Licencing is a little complicated as you can both purchase options via AWS for them to provide the licence or you can use your own.

If you have specific questions I should be able to help as we have been using many of the AWS products for the last 3 years.