Amazon CloudWatch & CloudTrail

It’s an Amazon web service that monitors the AWS resources and the applications you run on AWS in a particular region.
It enables monitoring for EC2 and other AWS services, so you can get alerts when things go wrong.
It collects and tracks metrics like it monitors how much traffic is coming to your instance, system-wise visibility into resource utilization, application performance, and overall operation health.
You can set user alarms to send notifications. Alerts can be sent to services like AWS Lambda, SNS, SQS, etc.
It automatically makes changes to the monitored resources, based on defined rules.

It’s a webservice that records AWS API calls for your account and delivers the log files to you.
Recorded information includes the identity of the API caller, time of API call, Source IP of the caller, request parameters etc.
It stores and delivers log files for you.
It provides a history of API calls for your account.