Ansible is an IT automation tool that can configure systems, deploy software, and orchestrate advanced tasks like continuous deployments. It uses a control node to communicate with managed nodes. To install Ansible on Debian, add the Ansible PPA, update packages, and install Ansible. Windows managed nodes require PowerShell 3.0+, .NET 4.0+, and a WinRM listener. The control node requires WinRM and pywinrm for communication with Windows nodes. Inventory files list hosts and groups for Ansible to automate.