• Collect and index any machine data from virtually any source, format, or location in real time.  Data can be any kind of machine data such as logs, application data, raw data from hardware and software sensors, user feedback data, survey responses, IoT device data, and more.
• Search and navigate machine data, through real-time, fast, free-form searches using five different types of correlation (time, transactions, sub-searches, lookups, joins) and interactive results.
• Gain operational intelligence by correlating and analyzing relationships within the data, across multiple sources, to facilitate event pattern detection.
• Visualize and report via custom dashboards and views, as well as scheduled reports, with interactive charts, graphs, and tables.
• Monitor and alert based on events, conditions, or key performance metrics.  Alerts can be sent to indicate emerging issues and abnormal conditions that enable administrators to take  preventative and proactive measures.
• Includes secure data handling, fine grain access controls, auditability, assurance of data integrity, and integration with existing authentication solutions.
• Add vendor supplied, community created and custom apps to enhance and extend the Splunk core features.

For a more detailed description of features and capabilities, see https://www.splunk.com/en_us/products/splunk-enterprise/features.html