You define a set of tasks, explain how they should run and on which servers, and run on a potentially large set of computers via SSH. Nothing is installed on the remote nodes you are targeting.

A typical scenario would be "install php on web servers, fill this nginx configuration template then push it to /etc/nginx/site-available/, make a link from /etc/nginx/sites-enabled, on database servers only install PostgreSQL, etc. etc."

I think this tool is promising, as ansible is quite slow and error-prone. But with software alternatives there's always the problem of feature coverage and community adoptions and support.