Calculated fields in Splunk are based on which of the following?

Calculated fields in Splunk are specifically defined using eval expressions. These expressions allow users to create new fields derived from existing fields within the data. By utilizing eval, you can perform mathematical operations, string manipulations, or conditional logic to yield new information that can be useful for analysis and reporting.

The importance of eval expressions stems from their versatility; users can apply a wide range of functions that enhance their data exploration capabilities. This enables users to create fields on-the-fly within their searches, which can then be utilized in visualizations or further calculations during analysis.

The other choices, while important in their own right, do not pertain specifically to the creation of calculated fields. Keyword searches focus on locating specific terms within the data, stats commands are used for aggregating data, and field extractions refer to the process of identifying and pulling fields from raw data. Each of these elements plays a distinct role in data processing and querying in Splunk, but it is the eval expression that is uniquely tied to the creation of calculated fields.