In a distributed environment, which Splunk component is used to distribute apps and configurations to...

The deployer is a Splunk Enterprise instance that you use to distribute apps and certain other configuration updates to search head cluster members. The set of updates that the deployer distributes is called the configuration bundle.https://docs.splunk.com/Documentation/Splunk/8.1.3/DistSearch/PropagateSHCconfigurationchanges#:~:text=The%20deployer%20is%20a%20Splunk,is%20called%20the%20configuration%20bundle.

https://docs.splunk.com/Documentation/Splunk/8.0.5/Updating/Updateconfigurations

First line says it all: "The deployment server distributes deployment apps to clients."