Trusted Advisor covers four main areas and it is designed to give you some guidance around what are considered best practices for your cloud deployment. The areas covered are:
Cost Optimization
Performance
Security
Fault Tolerance
It's available to everyone and free to use—with one fairly large catch. Unless you are paying for Business or Enterprise level support with AWS you only get access to four checks. At the time of publishing there are 55 possible checks.
The good news is you don't need to do anything at all to turn on Trusted Advisor. It's automatically enabled when your AWS account is created and will continue to update for the lifetime of your account.
Go ahead and navigate to the Trusted Advisor
section of the AWS web console.