https://docs.splunk.com/Documentation/Splunk/7.3.1/DistSearch/Howuserscancontroldistributedsearches
"From the user standpoint, specifying and running a distributed search is essentially the same as running any other search. Behind the scenes, the search head distributes the query to its search peers, and consolidates the results when presenting them to the user."

https://docs.splunk.com/Documentation/Splunk/8.2.2/Data/UsetheHTTPEventCollector
"The HTTP Event Collector (HEC) lets you send data and application events to a Splunk deployment over the HTTP and Secure HTTP (HTTPS) protocols. HEC uses a token-based authentication model. You can generate a token and then configure a logging library or HTTP client with the token to send data to HEC in a specific format. This process eliminates the need for a Splunk forwarder when you send application events."

https://docs.splunk.com/Documentation/Splunk/8.1.1/DistSearch/Forwardsearchheaddata Per the provided Splunk reference URL by @hwangho, scroll to section Forward search head data, subsection titled, 2. Configure the search head as a forwarder. "Create an outputs.conf file on the search head that configures the search head for load-balanced forwarding across the set of search peers (indexers)."

https://docs.splunk.com/Documentation/Splunk/7.3.1/Admin/Configurationfiledirectories Section titled, Configuration file directories, states "A detailed list of settings for each configuration file is provided in the .spec file names for that configuration file. You can find the latest version of the .spec and .example files in the $SPLUNK_HOME/etc system/README folder of your Splunk Enterprise installation..."