YML, YAML Document (.yml)
The YML Developer file format
YML files are used by developers as they contain source code written in the YAML (YAML Ain’t Markup Language) programming language. The code inside a YML file is human-readable and generally used to serialize data. With the help of a YML file, data can be read and written completely independent of programming languages. Thus, YML files can be used with many other files containing source code in different languages such as C, C#, C++, Java, PHP and more.
Technical details of YML files
Due to its versatility, YML files are used by a wide range of developers working with many different markup languages. One common use of a YML file is the database.yml file used by Ruby on Rails where it is used to connect to a database. Sometimes, these files are also stored as YAML files.