Amazon CloudWatch monitors your Amazon Web Services (AWS) resources and the applications you run on AWS in real-time.
AWS CloudTrail is an AWS service that helps you enable governance, compliance, and operational and risk auditing of your AWS account.

CloudWatch Logs

Collects custom logs from applications.

CloudWatch Metrics

Creates visual charts.

CloudWatch Alarm

Sets up alert conditions for logs to trigger subsequent actions, such as sending SNS notifications or triggering actions on other AWS resources via CloudWatch Events.

CloudWatch Agent

By default, cannot monitor memory and disk usage on machines and needs to be installed on the server manually.
Applications can also be written in a specified folder and then collected into CloudWatch Logs through the agent.

Monitoring Aspects

Server Operation Status

Each server sends logs to a separate log stream through the agent and then to CloudWatch Logs, facilitating monitoring of each server’s operation status.

Service Operation Status

By grouping multiple log streams into a Log Group , the overall operation status of the service can be evaluated.

CloudTrail

Tracks user activity and API usage: AWS CloudTrail

Used to record user operations on AWS, records can be stored in S3 and visual monitoring and notifications can be set up through the CloudWatch Logs service.