Each federated user, ie. a user which has joined the RosettaHUB through an institution, has a dedicated AWS account. As a user you access your AWS account via an IAM user that RosettaHUB has created for you at the creation of the account.
You can create IAM users and roles from the AWS console or cli. You can also create IAM users and roles from the RosettaHUB console, by default all users created from the RosettaHUB console have access to the AWS console, they can be easily shared and you can assign them bespoke IAM policies.
IAM users are useful if you want to give access to your account to other users or groups and limit what permissions they have on your AWS account. This allows you for example to give access to AWS to users who do not have an AWS account or to give access to a specific S3 buckets to a group of users.