Amazon web services: Where to start

Amazon Simple Storage Service (S3) is for load static content , maybe images, videos, or something you want to save, You could think of it like a hard drive for storage.

Amazon Elastic Compute Cloud: ( EC2) basically is your Virtual Operative System, you can install whatever OS you want (Debian, Ubuntu, Fedora, Centos, Windows Server, Suse enterprise). ( if your application uses server side processing this will be its home)

Amazon Simple DB, is a no-sql database system, that you could use for your aplications, and Amazon gives you as a service, but if you want to use something more, you could install yours on EC2, or use RDS for Database server (MySql for example)

If you want to know more, there are some books, like: "programming Amazon EC2" or see Amazon screencast at http://www.youtube.com/user/AmazonWebServices or its presentation on http://www.slideshare.net/AmazonWebServices