All AWS products are offered as AWS Services,so you can choose the services to meet your requirements, such as EC2(Elastic Computing Cloud), RDS(Relational Database Service) and many other services. Some of these Services are Global Services and some services may be available in some AWS Regions, reason for this is AWS may be rolling out that particular AWS Service to other Regions, but majority of AWS services are available across all AWS Regions.
Some of the AWS services are Global, meaning that they are available across globe irrespective of AWS region your are using. To identify whether the service is Global, when you choose a Service from AWS console, it appears on the right side upper corner of the screen as shown in below image.
AWS services available in each different region can be found here in this link https://aws.amazon.com/about-aws/global-infrastructure/regional-product-services/
Some AWS Services may be available only in specific reagion, there could be several reasons for this, like the service may not be rolled yet to that specific region or there are no customers wants to use that service etc. AWS general policy is that any new service or feature developed will be rolled to all the regions in 12 months of general availability (according to https://aws.amazon.com/about-aws/global-infrastructure/regions_az/).
When you choose a service from AWS Console, if the service is is not available it shows the below error 'Region Unsupported' and also shows which regions have that service available.
