It is written in an INI or YAML format, lists host and groups. Can be static of dynamic. Example of Collection of groups Dev:children # cat /etc/ansible/hosts [managedClients] [RHEL_Dev] lab-rhel-1 lab-rhel-2 [AIX_Dev] lab-aix-1 lab-aix-2 [Dev:children] RHEL_Dev AIX_Dev # ansible-inventory --graph @all: |--@Dev: | |--@AIX_Dev: | | |--lab-aix-1 | | |--lab-aix-2 | |--@RHEL_Dev: | | |--lab-rhel-1 | | |--lab-rhel-2 |--@local: | |--localhost # cat /etc/ansible/hosts [managedClients] [RHEL_Dev] lab-rhel-1 ansible_user=ansible lab-rhel-2 ansible_port=22 [AIX_Dev] lab-aix-1 ansible_host=10.1.1.1 lab-aix-2 [Dev:children] RHEL_Dev AIX_Dev # ansible-inventory –list …. "hostvars": { "lab-aix-1": { "ansible_host": "10.1.1.1" }, "lab-rhel-1": { "ansible_user": "ansible" }, "lab-rhel-2": { "ansible_port": 22 } ….