Final answer:
An IAM user must provide an access key ID and secret access key to interact with AWS services using the AWS CLI. These are used to sign API requests to AWS and are different from a username and password, which are used for console access.
Step-by-step explanation:
To interact with AWS services using the AWS Command Line Interface (AWS CLI), an IAM user must provide their access key ID and secret access key. These credentials are used to sign programmatic requests to the AWS API. Your access key ID and secret access key are similar to a username and password but are used exclusively for programmatic (CLI, SDK, etc.) access to AWS services.
Username and password are generally used for console login, which is not the method used by the AWS CLI. API keys are a more generic term for tokens used by various services and are not specific to AWS. Lastly, session tokens and security tokens are often part of temporary security credentials, which are not required for the main question unless the IAM user is assuming a role or dealing with federated user sessions.