Explanation:
Key Management Service: The use of AWS KMS is an optional element of CloudTrail, but it allows additional encryption to be added to your Log files when stored on S3 Simple Notification Service: Amazon SNS is also an optional component for CloudTrail, but it allows for you to create notifications, for example when a new log file is delivered to S3 SNS could notify someone or a team via an e-mail. Or it could be used in conjunction with CloudWatch when metric thresholds have been reached. CloudWatch Logs: Again, this is another optional component, but AWS CloudTrail allows you to deliver its logs to AWS Cloudwatch Logs as well as S3 for specific monitoring metrics to take place.
Reference:
https://cloudacademy.com/amazon-web-services/aws-cloudtrail-introdu…