What metrics can be monitored through CloudWatch without being charged?

Related questions

1. Is EBS ephemeral?
2. Where is EBS snapshot stored?
3. What is the underlying hypervisor for ec2?
4. What is an advantage of using Amazon EFS over Amazon EBS?
5. Can we attach single EBS to multiple ec2s same time?
6. What is the minimum size of an EBS volume?
7. Where are AWS ec2 snapshots stored?
8. How does EBS snapshot work?
9. Does Amazon charge for snapshots?
10. Can we attach EBS volume to more than one ec2 instance?

Tags

1. #monitoring
2. #cloudwatch
3. #stored
4. #intervals
5. #minute
6. #metrics
7. #weeks
8. #monitor
9. #amazon
10. #network
11. #collected
12. #instances
13. #charge
14. #additional
15. #basic