Security Information and Event Management (SIEM) is a centralized security monitoring platform that aggregates, normalizes, correlates, and analyzes log data from across an organization's IT infrastructure to detect threats, investigate incidents, and support compliance requirements. SIEM enables real-time threat detection by applying correlation rules and behavioral analytics to millions of security events, transforming raw log data into actionable intelligence that reduces Mean Time to Detect (MTTD) and Mean Time to Respond (MTTR). The most critical insight for SIEM practitioners in 2026 is that effective detection depends more on high-quality, well-tuned correlation rules and contextualized enrichment than on sheer log volume—a SIEM with 50 strategically selected data sources and precision-tuned detections outperforms one ingesting everything without purpose.