Ansible is an open source continuous configuration automation tool that allows users to automate the management of host systems. It can be used for various administration and configuration tasks such as installing and configuring applications, services, security policies, and other infrastructure-related tasks. Ansible can also be integrated with provisioning tools like Terraform to automate the build and deployment of infrastructure. Additionally, it provides a secure layer to infrastructure build and management by utilizing private Cloudsmith repositories, which offer access control and permission control. An Ansible playbook is a collection of tasks that defines the series of actions needed to achieve a desired configuration state on host systems. The playbook can be used to install and configure packages, including those from private Cloudsmith repositories, and can be run using the `ansible-playbook` command, which asks for sudo password input or uses Ansible Vault for encrypted secrets.