What is the effect of applying a filter to search results in Splunk?

Applying a filter to search results in Splunk primarily has the effect of reducing the number of events displayed, which is reflected in the chosen answer. When a filter is applied, it specifies criteria that events must meet to be included in the search results. Consequently, only those events that satisfy the defined conditions are shown, streamlining the output to improve focus on relevant data.

This is a common practice in data analysis and management to make it easier for users to interpret results by eliminating extraneous information. The remaining options all suggest processes that do not accurately reflect what a filter does within the Splunk environment. For instance, filtering does not modify the original indexed data—indexed data remains unchanged regardless of any filters applied to display search results. Additionally, filters do not create a new index or simply highlight certain events; rather, they work by refining what is visible based on set parameters.