AWS OpsWorks is an application management service that simplifies software configuration, application deployment, scaling, and monitoring. OpsWorks is recommended if you want to manage your infrastructure with a configuration management system such as Chef.
AWS Cloud Formation helps developers and system administrators by providing the easiest way to create and manage a large number of AWS resources, provisioning and updating them in an orderly and predictable fashion. By using cloud Formation in a few hours you can build up your large-scale environment from a single template.
AWS CloudFormation - Create and Update your environments.
AWS Opsworks - Manage your systems inside that environments as we do with Chef or Puppet
You can also refer to this blog: https://www.edureka.co/blog/introduction-to-aws-opswork/