Instances and Autoscaling group send ( or can send) data points to CloudWatch that we can monitor.

There are different types of metrics:

Basic Monitoring refers to Instances and have 5 minutes granularity.

Group Metrics refer to Auto Scaling Groups, have 1 minute granularity and are not enabled by default.

Detailed monitoring, are metrics for Instances with 1 minute granularity.

While Basic and Group monitoring is free of charge, for detailed instance monitoring you will have to pay a fee.