You can test-drive some services from AWS within certain usage limits at no charge. AWS calls this the AWS Free Tier. The free tier is designed to give you hands-on experience with AWS at no charge. For example, with the features in the free tier, you can investigate AWS as a platform for your business.
Note that if you don't use the full benefits provided by the free tier in a given month, they don't roll over to the next month. To maximize your benefit from the free tier, be sure to spend time with AWS each month, investigating the services that you're curious about.