Since using Codeivate I have been more curious about additional languages and code implementation. I like to look at what other users are coding in - which exposes me to new things I haven't heard about. This morning it was YAML, or "YAML Ain't a Markup Language".
It's a data structuring format for data serialization. You may being wondering what data serialization is too - well that is formating of content in a way that it can be accessed and reconstructed later. Probably the most popular serialization standard is JSON which is based off of Javascript syntax. YAML is actually a subset of JSON which means most YAML parsers can access JSON as well. You may be thinking that XML is a serialization form as well - It is, but it isn't a true serialization language like JSON and YAML, however XML can be used for serialization.
It looks like a bunch of properties tabbed. That's why YAML is really popular for configuration settings.
Some Resources