This is the endpoint URI used to collect data in a customer managed Splunk Enterprise environment. According to the Splunk documentation, the HTTP Event Collector REST API endpoint is /services/data/collector. You can use this endpoint to send events to HTTP Event Collector on a Splunk Enterprise or Splunk Cloud Platform deployment." You can also use this endpoint to send events to a specific token or index.

A network input is a type of input that monitors data from TCP or UDP ports. To configure a network input, you need to specify the port number, the connection host, the source, and the sourcetype in the inputs.conf file. You can also set other optional settings, such as index, queue, and host_regex. The inputs.conf file is a configuration file that contains the settings for different types of inputs, such as files, directories, scripts, network ports, and Windows event logs. The inputs.conf file can be located in various directories, depending on the scope and priority of the settings. The most common locations are:
$SPLUNK_HOME/etc/system/default: This directory contains the default settings for all inputs.
You should not modify or copy the files in this directory. $SPLUNK_HOME/etc/system/local: This directory contains the custom settings for all inputs that apply to the entire Splunk instance. The settings in this directory override the default settings.
$SPLUNK_HOME/etc/apps/$appName/default: This directory contains the default settings for all inputs that are specific to an app. You should not modify or copy the files in this directory.
$SPLUNK_HOME/etc/apps/$appName/local: This directory contains the custom settings for all inputs that are specific to an app. The settings in this directory override the default and system settings. Therefore, the best practice is to create or edit the inputs.conf file in the
$SPLUNK_HOME/etc/apps/$appName/local directory, where $appName is the name of the app that you want to configure the network input for. This way, you can avoid modifying the default files and ensure that your settings are applied to the specific app.

https://docs.splunk.com/Documentation/Splunk/7.0.3/Forwarding/Routeandfilterdatad#Perform_s elective_indexing_and_forwarding Specifies a comma-separated list of tcpout group names. Use this setting to selectively forward your data to specific indexers by specifying the tcpout groups that the forwarder should use when forwarding the data. Define the tcpout group names in the outputs.conf file in
[tcpout:<tcpout_group_name>] stanzas. The groups present in defaultGroup in [tcpout] stanza in the outputs.conf file.

https://docs.splunk.com/Documentation/Splunk/8.0.6/Updating/Deploymentserverarchitecture>
https://docs.splunk.com/Splexicon:Serverclass