Same basic concept as the others. Ansible has Playbooks to Chef's Recipes. Ansible has Vars to Chef's data bags, and template files just like Chef or Puppet. For some reason, Ansible just ends up being much simpler to get going with. Probably because you write playbooks in a very straightforward yaml syntax, and the topology is not client-server - you just run Ansible right from your local terminal, like running knife I guess, with chef-solo. Just look at the documentation on their site, there's basically 3 or 4 pages you need to read before you're writing playbooks. I've worked with all three, Ansible is far and away the only sane one if you ask me.