Hiera is a system for looking up configuration data in a format called "key-value." It helps get data out of the Puppet code. For explicit parameter lookup calls for classes from a catalog, this code uses this system. This system finds data sources by looking at Puppet's facts. Its 5th version can read JSON, YAML, and EYAML data files.  It looks for configuration data in three separate layers of configuration, starting with the global layer, then the environment layer, and ending with the module layer.