Ansible in its simplest form has been described as a Python-based open source IT automation tool that can be used to configure\manage systems, deploy software (or almost anything), and provide orchestration to a process. These are just a few of the many possible use cases for Ansible. In my previous life as a production support infrastructure engineer, I wish such a tool would have existed. I would have surely had much more sleep and a lot less gray hairs.
One thing that always stood out to me in regard to Ansible is that the developer's first and foremost goal was to create a tool that offers simplicity and maximum ease of use. In a world filled with complicated and intricate software, keeping it simple goes a long way for most IT professionals.
Staying with the goal of keeping things simple, Ansible handles configuration/management of hosts solely through Secure Shell (SSH). Absolutely no daemon or agent is required. The server or workstation where you run the playbooks...