The .spec file also specifies what are valid settings for the stanzas. When Splunk starts it will check your conf files and compare them with the appropriate spec files. If you have options that do not exist in the spec you will get warning messages.
Generally .spec file specifies the syntax, including a list of available attributes and variables. A configuration file may have .spec and .example files under README dir for reference purpose .The .example file contains examples of real-world usage.
Splunk Enterprise configuration information is stored in configuration files. These files are identified by the .conf extension and hold the information for different aspects of your configurations.