Reference:https://docs.splunk.com/Documentation/Forwarder/8.2.1/Forwarder/Configureloadbalancing

According to the Splunk documentation1, a heavy forwarder is a Splunk Enterprise instance that can parse and filter data before forwarding it to an indexer. A heavy forwarder can perform line breaking, which is the process of splitting incoming data into individual events based on a set of rules2. A heavy forwarder can also apply other transformations to the data, such as field extractions, event type matching, or masking sensitive data3.

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."

Reference: https://docs.splunk.com/Documentation/Splunk/8.0.5/Security/Secureyouradminaccount

Indexers, search head, deployment server, license master, universal forwarder. This is the combination of Splunk component instances that are needed to handle the volume of data from collecting log files from 50 Linux servers and 200 Windows servers, following the best practices. The roles and functions of these components are:
Indexers: These are the Splunk instances that index the data and make it searchable. They also perform some data processing, such as timestamp extraction, line breaking, and field extraction. Multiple indexers can be clustered together to provide high availability, data replication, and load balancing.
Search head: This is the Splunk instance that coordinates the search across the indexers and merges the results from them. It also provides the user interface for searching, reporting, and dashboarding. A search head can also be clustered with other search heads to provide high availability, scalability, and load balancing.
Deployment server: This is the Splunk instance that manages the configuration and app deployment for the universal forwarders. It allows the administrator to centrally control the inputs.conf, outputs.conf, and other configuration files for the forwarders, as well as distribute apps and updates to them.
License master: This is the Splunk instance that manages the licensing for the entire Splunk deployment. It tracks the license usage of all the Splunk instances and enforces the license limits and violations. It also allows the administrator to add, remove, or change licenses.
Universal forwarder: These are the lightweight Splunk instances that collect data from various sources and forward it to the indexers or other forwarders. They do not index or parse the data, but only perform minimal processing, such as compression and encryption. They are installed on the Linux and Windows servers that generate the log files.