This tutorial presents Ansible step-by-step. You'll need to have a (virtual or physical) machine to act as an Ansible node. A Vagrant environment is provided for going through this tutorial.
Ansible is a configuration management software that lets you control and configure nodes from another machine. What makes it different from other management software is that Ansible uses (potentially existing) SSH infrastructure, while others (Chef, Puppet, ...) need a specific PKI infrastructure to be set up.
Ansible also emphasizes push mode, where configuration is pushed from a master machine (a master machine is only a machine where you can SSH to nodes from) to nodes, while most other CM typically do it the other way around (nodes pull their config at times from a master machine).
This mode is really interesting since you do not need to have a 'publicly' accessible 'master' to be able to configure remote nodes: it's the nodes that need to be accessible (we'll see later that 'hidden' nodes can pull their configuration too!), and most of the time they are.
This tutorial has been tested with Ansible 2.7.1.