Access tokens are credentials used to access protected resources. You can get an access token in according with the OAuth 2.0 Authorization Framework. In general, there are 4 grand types/ flows defined in the OAuth 2.0 Authorization Framework specification. The Cognito access token is also represented as a JSON Web Token (JWT). If you want to use access token, please make sure one of grand types is implemented in your application accordingly.

In terms of Access Keys, Cognito identity pools assign your authenticated/ unauthenticated users a set of temporary, limited privilege credentials to access your AWS resources by using Role-Based Access Control Principle. The unauthenticated users are controlled through IAM roles that you create for the user without a valid login. Access keys consist of two parts: an access key ID (for example, AKIAIOSFODNN7EXAMPLE) and a secret access key (for example, wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY). Like a user name and password, you must use both the access key ID and secret access key together to authenticate your requests.