Explanation:
Configuration management (CM) tools are great at the config nodes but less good at coordinating complex tasks. Orchestration tools tend to leave configuration to specialist tools.
Traditional server environments are mutable, in that they are changed after they are installed.
Administrators are always making tweaks or adding code. CM tools evolved to manage this complexity and bring order to the configuration and updating of tens to thousands of servers. An immutable infrastructure is one in which servers are never modified after they're deployed. If something needs to be updated or changed, new servers are built afresh from a common template with the desired changes. This is the world of Terraform, where new servers replace the existing servers. This is also the philosophy of containers. With orchestration, immutability is easily applied to servers as they usually have built-in support for managing the lifecycle of a resource from creation to tearing down.
Reference: https://www.ibm.com/cloud/blog/chef-ansible-puppet-terraform