What is minimally required for Ansible to work with remote servers?

To minimally operate Ansible with remote servers, the following are required:

• Ansible installed on the control machine.
• SSH access with keys (passwordless for automation) on remote servers.
• Python installed on remote servers (usually Python 2.7+ or Python 3), as Ansible uses it to execute modules.

Thus, at minimum: a control machine with Ansible, SSH access to remote hosts, and Python on those hosts.

Example connection:

[webservers]
server1.example.com
server2.example.com

And running the command:

ansible webservers -m ping