Security Information and Event Management (SIEM) is software that improves security awareness of an IT environment by combining security information management (SIM) and security event management (SEM). SIEM solutions enhance threat detection, compliance, and security incident management through the gathering and analysis of real-time and historical security event data and sources.
SIEM’s main capabilities provide a broad range of log event collection and management, increasing the ability to analyze log events and other data across dissimilar sources, and operational capabilities including incident management, dashboards, and reporting.
SIEM also offers data aggregation across the enterprise network and normalization of that data for further analysis. Additionally, SIEM helps enable security monitoring, user activity monitoring, and compliance.
https://www.mcafee.com/enterprise/en-us/security-awareness/operations/what-is-siem.html